I would have a bpm setting per scene as option
Yes you can but that’s 4, not 8Would be handy.
As a possible work around, Tempo is part of the Controllers, which is like a hidden block in each preset. That block has 4 channels like most other blocks, so you can actually set a different tempo for each of the 4 channels of the Controllers block and change that via scenes. Keep in mind though that the channel affects all of the controllers together, so changing channels there will give you separate settings for all of the controller types at once.