I think star difficulty based categories for 1*, 2*, 3*, etc would bring players of a specific skill level to speedrun osu! Just a suggestion.

But does a 1 star map still counts as a 1 even if I put dt on it and it changed to 2?

No, it should be star difficulty specific. 10 1* FC's or 10 2*FC's with and without mods can be considered. Maybe it could be added in a category extension pack.