Like the idea of islands more, though would recommend to take moons of ardaan as design sample instead of anno. Anno is a bit strange, where houses are split from production, while moons of Ardaan have interesting concept where you need build cities to satisfy worker requirement, I understand that you settle your girls and put them into work as before, including gear, so it probably close. Though still find my biggest problem is I need to fight constantly same battles to clear land for building. But I love this more than enchanting where you had to breed or capture shit ton of rare species just to burn them. This way you reduce tedium, yet still keep progression because you still need to be able to provide for better warrior training.
Land itself is maze like and does not have enough building freedom like in Anno, so when I try to put houses then entertainment buildings then other bonus stuff I realize there is not enough space to fit it in with road requirement. So I feel those adjecent or near buildings are not well fit into game though it is maybe me. Also would make most satisfying needs buildings workerless, or maybe ghost workers where you put populace in general no levels, and then need to supply bondage of certain kind to keep effects so you can have generic puppet fit in bondage to depict workers.
As for lockable equipment from enemies? dunno considering amount of fights you need to do outside it might become even more annoying, even if it timed. would end up to people getting trainings to remove equipment as fast as possible and using it. Maybe if one of party members are defeated they can keep all gear or even get few more once you rescue them or they return. Or if you have less fighting but it is more meaningful and helps with leveling. (Regular exp is also a bit boring, liked ero dungeons one, but have you thought something like medal system. You split all levels, on class/race/generic/quirk/location/enemy category, and then in difficulty. Then if one of girls acquired one of medals you get a level, you can acquire limited amount of medals per dungeon in one go. And you may make them in increasing difficulty, probably generic like fight x times, win x battles, kill x enemies are easy, class and race are a bit harder and need setting up class build and location enemy luck based but you would get them, and quirk well they need character to do something strange like be kidnapped x times. Offcourse each medal acquired only once so once you done with easiest, you either content with what you have or wait for late game options to acquire random medal in expensive way forgoing fight (which kinda replaces current training, and works similarly. Could even give trainings by category and split between different tech levels, or each medal being attached to skill active or passive like it is now, and unlock it) If you split difficulty in interesting way you might get a bit interesting progression and need to vary party just to level your team, and less fights means less annoyances of switching party members. Though medal system might also be hard to balance. Even if it is not used in this game feels could be interesting way to level up in some other game should it happen.