Small addendum - Strive 1 had futa with/without balls option. I suggest you handle both kinds the same - given them both balls, just alter or hide the description for balls ones, since balless actually means scrotumless. Even Strive 1 mentions they have internal balls. Will also cause less issues with future modders.
The UI definitely has issues with too much clicks. I can already see some easy fixes. will elaborate more later.