I think that aside from figuring out how to adjust the Ability score increases out of the monsters if they are included in monster stats, that any other thing I feel should be optional will be easy to separate from Basic without negatively impacting the core math of the game.
With that out of the way, I really like what the folks at WotC have done with Fifth Edition.
I had some concern about all classes having an identical increase in combat value, however I have been reading a lot of reviews and some people willing to dig deeper into the system pointed out how much more powerful a fighter gets in melee combat through class capabilities than the other classes. The classes really do break out nicely into their own respective niche.
While I have not had a chance to run or play yet, just a read through the magic/spells has me anticipating the fun of experienced players trying to relearn how a few things work in order to churn out some seriously cool uses for spells and spell combinations.
That's all for the moment. After a long day of work . . .