In addition to the reinforcement restrictions, there is also a "Can be used in waves" flag and a Exowave flag. Those you can see by exporting the unit list from the game - there are also touched up, more readable versions attached somewhere here on the forums. Just look for the WaveName and EventAttackTier columns - if there isn't a value there, that unit cannot be used for that sort of thing.
I saw that option only exports units available to Human players. I managed to somewhat circumvent that restriction with the "give me positively everything" cheat, but there are still AI units, for instance, that I wasn't able to get by this way. The F1 key is paramount for wiki work, but sometimes details like these aren't easily available.
Also, still thinking about AIW2, I'm looking for a way to improve that. IMO, AIW's main problem is its learning curve, and its learning curve's main problem is the game incoherency (not complexity... not only complexity). One of my ideas was to move all the ships with cap < 10 as starships. They already have tons of starship immunities. As AI better handle caps with starships (at least it use them without too much abuse), I think it would elegantly solve that problem. They would be "high cap starships" (5 or 8 per mark). (And also make the game much more coherent by respecting its own rule "low cap -> starship / high cap -> fleetship", but that's another story.)
So. Does someone knows the rule for starship restrictions? They are used as reinforcement and in waves but in reasonable quantities. I would be totally okay to have TLD and Blade Spawners at the "starship rarity". Even, maybe, the AI could get 2 cap-5 or 3 cap-8 units where it would normally get 1 cap-2 true starship.
Also, drone spawning starships (Neinzul Starship and NCC) seems to be forbidden for the AI to use. It's strange, IMO, because they seem to be units more useful in the hands of Human players (contrary to, for example, cloaked units which are more dangerous in the hands of the AI). I'm currently in a game where an AI has Sentinel Frigates (could have been Snipers, for that example) and it "cleverly" use them, keeping them in the back while other units charge their prefered targets and the bombers rush for FFields and OCStation. I know there is a "shield basher" flag for units somewhere deep in the game; Senith Siege Engines have the same logic as Bombers, for instance. I bet there is a similar "long range siege" flag (or easily could be one) for Sentinels, Snipers, and potentially AI Neinzul Enclave Starship and NCC. And I would totally be ok with AI (fast/slow) drone spawning units provided the AI doesn't (ab)use them more than starships.