Personally I think you're looking at something that's going to be an expert or even master class benefit.
Problem is that the alternative is 'extinct species'. The only
way that monkey tribe would let them survive is if they could disguise themselves as monkeys. We are
the Bandar-log. (Yeah, I know kinda flies in the face of standard fantasy fare - but we have enough difficulties with other humans that 'look different'.) Drakes would be one of the hidden species, who never left. Others are some (not all) goblins, and rootwalkers (Ellum do grieve, oak he do hate, willow do walk if yew travel late - Devonshire
saying). Faeries have just sort of 'faded' and are only now returning, with none able or willing to answer where they had gone. (Some few had remained, but they were very few, and at one time very powerful fey - along the lines of the Puck and the Trash Hound.)
Also, too many of the dragons of legend could
use tools, even in Germanic myth - Fafnir coming to mind. I do agree that gaining thumbs in Drake form would have to be an advanced feat, most likely requiring X Species feats. Come to it Fafnir was also a shapechanger (and a dwarf...).
In human form I would definitely strip them of all Species and abilities, But given that Drakes would
be this world's dragons the ability to shape change is endemically a part of the myths. The possibility of doing it along the lines of 'Build an NPC using 50 XP as your human form' might be another consideration.
The Auld Grump