if you don't get permission from every person you use the charts of then I strongly dislike the idea, even better again if you can try to use featured artists.
it's basically impossible to actually balance since skill is such a subjective thing and i'd say leaving long note and rice separate is a much better idea just because of how they are so much different.
regardless of what you do they will be controversial and people will be quick to tell you every mistake because people are tired of the dan courses being the only thing the entire community talks about or plays, also dans are really only a big part of osu!mania in particular, bms has them but it's just not the same as in osu where it has completely taken over the community as a whole, there is a reason neither of the people who made the other dans want anything to do with them anymore
it's basically impossible to actually balance since skill is such a subjective thing and i'd say leaving long note and rice separate is a much better idea just because of how they are so much different.
regardless of what you do they will be controversial and people will be quick to tell you every mistake because people are tired of the dan courses being the only thing the entire community talks about or plays, also dans are really only a big part of osu!mania in particular, bms has them but it's just not the same as in osu where it has completely taken over the community as a whole, there is a reason neither of the people who made the other dans want anything to do with them anymore