I'd like to try a dedicated missile spammer but it seems like even the modders shy away from making something that vomits a million missiles across the map.
Grab the Hiigaran Descendents, get yourself a Kuun-Lan Battlecruiser or Vanaar Cruiser, and fit them out with Abas missiles - they automatically reload over time, and the Kuun-Lan's active ability significantly reduces missile reload times (the Vanaar just has flares). Catch is the Kuun-Lan's system generates unhealthy amounts of flux and Abas TAMs are energy damage so they're not particularly good against anything (having another ship to drop the target's shields with kinetics and then using HE missiles is far
faster for kills), though they aren't particularly
bad against anything either.
Still, if you push it to the limit with skills and/or a couple of good officers you can have dozens of missiles flying at a time, which is fun.
Alternately the ARS/Legacy of Arkgneisis
Donovan-class hull has a Missile Autoforge which can replenish
any missile system, but disables weapons whilst active and likewise generates a lot of flux. Eight small missile mounts makes for quite a bit of missile spam.