the skill revamp of 0.8 will greatly reduce the OP differences between base and skill-boosted ships, so i don't think this will remain much of a concern. currently, a high level player ship has 30% more available OP and roughly 20% decreased weapon OP costs. in 0.8, a skill-boosted ship will only have 10% more OP than base, and no weapon cost reduction at all. base OP of all ships will be slightly buffed to partially make up for this, but that will of course affect all fleets equally, not just high-level player fleets.
and i gotta say, i don't like the idea of buying ships with a fixed loadout, where to change any part of the loadout (besides weapon groups) i would have to give up a significant power boost. and sure, i could just not buy those ships (and i really probably wouldn't), but since those ships would be objectively more powerful than player-configured ships, not buying them would mean i'm intentionally gimping myself. that's assuming those loadouts themselves actually make good use of their OP.. but if they don't, being both suboptimal and unchangeable would completely defeat their purpose.
and just making them more expensive than buying the unfitted ship and the used weapons individually is not a good way to balance their power, if that's their only drawback (from a balance view).