If you have time/interest, I'd love to learn about an example of how you think about introducing another breed to improve a main breed.
When I'm crossbreeding, I only use rabbits that have something my purebreds need that I can't get due to the relatively; for instance, I used a Californian doe to improve the flesh condition, growth rates and muscle tone of my Satins. It worked

but it took four generations afterwards to get back to "purebred" Satins. (I like to register my brood stock, and have purebred rabbits to offer other breeders.)
I also - in general - avoid crossing to breeds that have recessives that could pop up later (like a satinized coat, in my Champagnes). I did actually recently do this cross (Champagne x Satin) because it was the best option I could find to improve health, temperament and depth over the loin in the Satins. I also used a Satin with one of Champagne does. I am prepared to eventually see unshowable satinized Champagnes and deal with them appropriately (they are meat rabbits, after all). I am getting good results with a Champagne x New Zealand cross, though, and will not have to cull satinized coats later. And, because Champagnes are a silvered self black, I used a NZRed, so litters will eventually have blacks (Champagnes if silvered, NZBlacks if not), as well as chestnuts (which can be shown as Argente St Huberts if they're silvered), oranges (which can be shown as Creme D'Argents or NZReds if not), and torts (unshowable in either breed, but still a nice meat rabbit).
For Jersey Woolies (a breed I love), I have a wonderful buck who is great in almost every way. But he's big for his breed and has long ears. No DQs, just "on the big side / long side." So in the grand scheme of things, that's where a well-typed fuzzy ND could contribute. And for my herd and fiber interests, just the buck and his beautiful fur is a welcome addition.
It sounds like your buck may be a false dwarf. If a false dwarf buck is a good example of the breed (other than the size, of course) he can be quite useful in a breeding program, if he's bred with a true dwarf doe, . Most folks like a false dwarf doe x true dwarf buck for other reasons, but I'd certainly try the buck. If you breed him to a true dwarf JW doe, the dwarf allele that some of the bunnies should get from the dam will probably solve the size problem. If you are especially interested in the fiber, and he has it, I'd certainly find a place for him.
You could use him with the fuzzy ND, but if you're trying to preserve the wool quality and/or other uniquely JW characteristics,, that might not be so helpful. I've found that rabbits with recessives that just suddenly pop out are usually lacking in important ways - over the generations, no one has been selecting, for instance, wool quality (this is true for many other modifiers, e.g. agouti ring color, rufus modifers, color intensity, etc.)
If he is not actually a false dwarf (has he ever produced a peanut?), breeding with a carefully selected true dwarf doe could still give you good bunnies.
If it was me, I'd take him to the best true dwarf JW doe I could find (and maybe also the fuzzy ND doe, just to see what comes of it).
There is a difference between introducing a new breed to improve or center the next gen on the SOP and mixing breeds to produce something new. I'm up for both. I know some people would never consider that latter, but in meat-breed realm, it's common. I think if you have a clear goal and do your research and stay honest and realistic, go for it. But see previous comment about not taking my advice!
I'm up for both as well. My Argente St Hubert project is the latter. The breed is currently being developed; St Huberts can be shown "Exhibition Only" now, and are awaiting their second pass at an ARBA Convention (hopefully this October). So, I am showing them up here, and hoping to generate some buzz and positive feelings among the visiting judges, especially those that are interested in the breed.
I started with the NZRed x Champagne cross to try to eventually get some Creme D'Argents with improved type, but on the way I got these St Huberts, and decided I liked the St Huberts even better than the Cremes. So, I am woking both to improve a currently recognized breed, as well as help develop a new one.
It is indeed observing how terrific the mini-satins and mini-rexes (and Jersey Woolies) are and knowing that there IS an urban and suburban fiber-artist market that led to my mini-angora project. Pretty sure it's not just me that wants a fiber pet, small but not too small, and
bred for excellent spinning fiber.
That last is the functional distinction between my mini-angora goal and Jersey Woolies. Some Jersey Woolies
happen to have great fiber for spinning and yes, the standard calls for length and density. But I believe that many JWs are being steered toward "low maintenance" coats. That's cool, and exactly what some people want. But not me.
There is a good number of breeders up here that raise rabbits for fiber, including the big angoras and the JWs (no AmFuzzyLops, though). They seem to agree that the JWs have spinnable fiber - some really like it - but that it's
not like French (or Satin or English) fiber, and that the JWs are definitely bred for ease-of-maintenance rather than other fiber qualities.
Distinct from Jersey Woolies is easy: the brachycephalic rabbit head shape must be recessive. I believe the short ears are too. So out of the gate (F1) the kits of a purebred French Angora and a purebred Jersey Wooly look like a French Angora. I'd also go a bit bigger than Jersey Wooly.
The round head and very short ears are mostly from the dwarf allele <
dw>, which is partially dominant (one copy makes a dwarf, two copies are lethal). There has probably been some selection for modifiers that produce relatively short ears and a shorter head in the rabbits with normal alleles <
DwDw>, as well. I had some Rex that had Mini Rex in the far reaches of their past; they were not dwarfs and made Rex weight; they could be shown as Rex, but many of them still had slightly shorter ears relative to the Rex that were not from that line. But as long as you choose the false dwarfs from a French x JW cross, and get rid of the dwarfy rabbits, you should get French-looking and bigger rabbits.
This is my draft breed description. It's pulled together from the descriptions of the constituent breeds, just like the rabbits are.
Mini-French Angora
This small breed is known for its wool qualities, and is docile and friendly. The wool is dense, strong, free falling, and evenly balanced over the entire body. The guard hairs are coarse and stand above the heavily crimped underwool. The ideal wool length is at least 3 inches.
It has an oval head set close to the body. The eyes are bold and bright. The ears are straight, set high on the head, and carried erect with or without tufts of wool.
The body has a compact type profile, with a full chest and round shoulder. Legs are
medium boned and well covered with good quality wool. The tail is straight and well
covered with wool. Wool color is rich and consistent.
Mature weight: Bucks and Does 4-5.5 pounds.
I like it! That's a nice size, and eliminating the dwarf gene will elimnate the unpleasant issue of having peanuts in the litters, which is very unappealing to many.
You might think about contacting someone at the national Angora breed club
https://nationalangorarabbitbreeders.com/
There may be some other angora breeders who like the idea, or even be working on it already, who might be interested in helping. It is often easier/faster to produce improved animals if you've got more breeders involved (adding many more options for brood stock, more cage space than you have in your own barn, and a greater variety of genetic material than one barn could contain).
The NARBC has a page dedicted to CODs (Certificates of Development, which is the first step toward obtaining ARBA recognition for a new breed, or new variety in an existing breed).
https://nationalangorarabbitbreeders.com
You don't have to enlist the support of the national breed club to develop a new breed or pursue a COD, but it can be helpful to be in contact with breeders interested in the same things you are, who can provide valuable insights or even brood stock.
The ARBA publishes a page outlining the COD process here:
https://arba.net/wp-content/uploads/2019/01/COD_Packet.pdf