Okay here's the thing, I will make entirely fanfic with a style similar to "Epic of Leviathan" or "Ascension or journey from world to world" where first world going to be Mushoku Tensei or maybe My Hero Academia. Though, my memory is a bit hazy with the story still consider this idea.
if Mushoku Tensei then I won't get Rudeus harem, Only Roxy and Ghislaine with Eris(not sure) . Yes, I'm reducing the harem for each world and Yes, The mc going to Rudeus Twin.
if MHA then I'll only get two girls undecided.