For full classes, this game will feel incomplete to me without Artificer being an option. "But it's not set in Eberron." So? That doesn't matter. Just because there's not already a place full of people doing what artificer's do as a commonplace thing doesn't mean there can't be some people out there trying to do such things. The only distinction would be that it doesn't look as advanced as you'd expect of an Eberron setting. Heck, you could even justify random enemy goblin artificer's where there creations would be jurry-rigged out of scrap. The very class page for Artificers already states they're found throughought the entire DnD multiverse, not just the Eberron setting, which can easily include this game. Honestly I don't rightly get where's there's so many people out there who think Artificer = Eberron only, thus causing me to add these extra sentences. But maybe the people causing that aren't in the BG community anyway, idk.
Regarding subclasses, especially considering all the Illythid involvement, I would *really* want all the more "lovecraftian" subclasses. Aberrant mind being the first to come to mind, pun half intended.