I have checked out Level Up and there is a lot to like. It's also possible to treat it as quite modular, so I am going to use expertise as a die roll, the basic combat manoeuvres, and some of the class features as alternates like in Tasha's. The armour rules are interesting but I worry they are too fiddly for our advanced age. I think my group is too long in the tooth to learn a full system that is similar but different.
Level up does have a couple of 3-step feat trees that double as prestige classes (arcane archer and shadow assassins spring to mind). That might be one relatively easy way to do higher level prestige classes, albeit as they stand, you are not obliged to take all three and with feats at a premium, it is a bit of an investment even if they give a lot of bang for their buck.
I was also toying with the notion of allowing extra attunement slots at higher levels maybe an extra common one and later an uncommon one. I'm not sure I would want to allow better than that, since freeing up lower slots means you take take extra improved items anyway. Not sure that there are many common items that require attunement mind you. Maybe it should be extra common at 5th, upgraded to uncommon at 10th, upgraded to rare at 15th plus an extra uncommon slot?
Level up does have a couple of 3-step feat trees that double as prestige classes (arcane archer and shadow assassins spring to mind). That might be one relatively easy way to do higher level prestige classes, albeit as they stand, you are not obliged to take all three and with feats at a premium, it is a bit of an investment even if they give a lot of bang for their buck.
I was also toying with the notion of allowing extra attunement slots at higher levels maybe an extra common one and later an uncommon one. I'm not sure I would want to allow better than that, since freeing up lower slots means you take take extra improved items anyway. Not sure that there are many common items that require attunement mind you. Maybe it should be extra common at 5th, upgraded to uncommon at 10th, upgraded to rare at 15th plus an extra uncommon slot?