Hiya!
I read most of it, up until you started going on about Feats. IMHO, taking Feats into consideration as a "base line" is akin to saying "Looking at races, we need to consider players going into town to buy any specific magic item to give their character an edge". The concept of "buying magic items" is firmly in the hands of the DM and is not assumed...kinda like Feats. Obviously (or probably?) you aren't going to be looking at characters with Gloves of Thievery, Gauntlets of Ogre power, Ring of Flying, Cloak of Invisibility, etc.
So, IMHO, you shouldn't be considering Feats, Multiclassing or any other "optional" things as the baseline. Once you've looked at the game from the "true" baseline (pretty much the Basic Rules; so no Barbarians, Bards, Drow, etc) and have that down...then you can go into the non-Optional stuff in the PHB. And then you can go and add in the effects that using Feats may have, or allowing Multiclassing, or what effects certain 'powerful/versatile' magic items may have, etc.
Jumping straight into using Feats (and, I'm going to assume Multiclassing) destroys any sort of "objective balance theorizing" because you are starting with a tainted sample.
^_^
Paul L. Ming