To me, the purpose is to buff the AI by making it engage with the mechanics better; the less we are called upon to "ignore the man behind the curtain", the better.Flat +100 seems better than 0 if the entire purpose is to buff the AI.
Under my axioms, which may not be your axioms, teaching the AI to ignore cap (well. sort of. it should probably pay attention to it in reverse, by not upgrading existing starbases to the next higher size if it still has cap to use up and systems to use it in.) when deciding whether to upgrade a starbase that already counts against the cap to a higher tier seems far and away a better choice.