MOD Question

[Suicide Junkie]

There is no way to limit technology to a particular shipset choice, but you can do the racial tech thing as Narf mentioned. Any race willing to pay the points will then get your extra ships/units sizes.

Alternatively, and what is usually done:
you can give everybody the extra ship sizes, and set the primary image to the neostandard name while the secondary image is a stock picture name.

That way, the races will for example use the "scout" image if they have it, and otherwise will just use the "escort" image or perhaps the large fighter if your scouts are really small.