well yuri mode dose not prevent M/F so why would that change? so yuri mode or not, if you lose, you lose some gold, OR you seduce the person who beat you and you ether go into the full sex mini game or give a brief dialog of what they did to you, and you keep your money(and maybe restore some MP) as long as we the player get the OPTION to seduce them, or lose money..only the rape fetish would complain, and EVERYONE else will be happy(hell maybe you can give us two options on lose, seduce for normal sex or submit for dom/rape)...
and maybe if they get high enough lust, like you said you can seduce them into sex mid fight..or maybe lose or over lust them, if you still got mana you can use the spell to change them to the other gender so even the Yuri fans cant complain and the hetro fans will still get their M/F
also i had an idea for the Yuri mode, it dose not prevent you from sleeping with men but maybe it could alter dialog and mechanics if you do, like the Iris is a reluctant lesbian, she will let the man have his way(even if you are still in control of the actions) but she gets no pleasure from it(and cant orgasm) or maybe some acts are locked out as her lesbian body simply can not accept it, so she can only do things like hand,boob,foot and blowjob. and dialog about me will show how she dose not like them,like no talk about "ohh hes so sexy" instead we get things like "im sure a normal woman would like him" and sex dialog can read as something like "its so gross...but i need the mana" "i hate every second...but at least its just using my hands"