DaedalusX51
Explorer
First, wow! That's a Looooooot of work. So kudos on that.
Haven't given it a full/thorough read. But really like what I saw.
I would say/recommend/suggest that you could continue to advance level and continue to advance the Proficiency Bonus. The increasing prof bonus can help with handling higher level threats without necessarily "overpowering" the characters or relying on magic items. Also there are a few various class features that use prof. bonus and those getting an occasional bump will help with the advanced level feel without having to add more features and more HD and more , more, more. I agree 5e can be a bit too much over too many levels.I've never been a fan of the "I can't have a 'dead' level! wah wah. bad design. wah wah. how pointless." So this looks like it could be a ton of fun.
I'm noooot 100% on making druids only Forest Gnomes. I might have made them a "subclass" of Half-elf. Or, rather, make the Half-elf the druid and make the bard a potential subclass thereof. Go back to 1e.
As for your Monk conundrum...in addition to being out of PHB classes to use...if you want to go back to a D&D race-as-class type game (but are including gnomes, half-elves, half-orcs, dragonborn and tieflings) I might suggest using Rakasta.
I know Tabaxi are in that new Volo's guy for monster characters. Not sure if rakasta are. But they could be easily skinned from tabaxi (HA! Skinning a cat...I crack me up). So, that was my first thought there. Go backs back to "Expert," instead of "Basic," but I think you could get away with it.
Thanks! I agree about the Forest Gnome Druid. I had trouble fitting that one in there. I can probably just make the Rock Gnome Illusionist just Gnome Illusionist and add another Elven like race.