Feature of 'combat' system (aka mid to lategame gameplay)

So I've been crackling my head for past few days to figure out what do I want in gameplay besides basic mansion management and exploration and finally got somewhat valid idea. Now, I'm really trying not to rip off ideas from any other developer but occasionally I do feel like I'm getting into that territory.

Anyway, right now there's 3 'physical stats' for any girl, which are strength agility and intelligence. Those affect income and outcome of few tasks and can grow. There's also limit for each girl on how high it can get based on race and age or preemptive generation. That's very sandboxy system which does not really work with game progress is what I realize now.

Firstly stat growth will be heavily limited to special tasks and training while still influencing income of standard tasks and will be way more restricted based on where you acquire certain girl. What I'm saying - stronger girl = greater stats to work with. And for stronger girls obviously you'll need to work harder (progress further).

Now what do we do with those cool grills which we payed our time? Well, firstly there'll be ranks/jobs/professions, like 'warrior rank 3' or 'cleric rank 5'. To have girls make it to there you'll need to pay and have necessary stats for her (I'm still in doubts about what stats will be added or removed though). Once she gets the rank, she can be assigned on a mission of various degree, like helping a town with bandits, or working as a nurse or roam into dungeon, that kind of stuff. Then, based on ranking and stats you'll see the outcome of her mission. The greater she is, the more positive it is. Naturally different missions will require different ranks to be optimized, and if your girl does not fit, disastrous and naughty events might occur.

Missions will reward you (and girls) with exp, money and loot, which is used for crafting and occasionally even new girls.

Now that's a lot to wrap my mind around and I have to consider how normal tasks will affect all that + what should be a good amount of servants to keep, although technically I'm limitless on how many of those can be there. The biggest part, naturally, make up that many missions, but that is for later, for now I have to replan and rewrite stat system.