Perhaps it is just my computer, but your formatting seems to have disappeared. Let me re-list your suggestion, to see if I have the right of it (and, of course, comment)...
Tax Rate
Beauty weighting for random girls
Max Traits loaded from file (or created for random girls)
Customer frequency
rival aggression
To the overall idea: I don't see why this would be a *bad* idea, although if everyone customizes the game to their liking it might make balancing an issue.
Going down the list...
1) Sure. Simple difficulty modifier, especially since (as has been stated elsewhere, by lots of people) money is basically a nonissue right now since it's so terribly unbalanced.
2) Meh... I wouldn't focus on just randoms, if you're going to do this. I've talked about this slightly in the thread for this, but basically my opinion is to alter it for all girls or not at all.
3) Maybe. Depends on your implementation. Would you take a random set from the givens, or just the first few? Would this include a total cap?
4) I, personally, wouldn't mess with this too much since customer frequency is already modified by lots of things, several of which I suspect are buggy.
5) I'm not entirely clear what you mean, here... would you just be increasing attack frequency? How about power of attacks? Overall rival power? First date of attacks? Number of rivals? Frankly, rivals are pretty ignorable at the moment, which is ironic considering they're the "victory" condition.