Crude Simulation Engine - New basic class design philosophy

Looking at how various old school derived and inspired games treat classes, I go back and forth about how I should structure these things in CSE.  There seem two be two basic philosophies:  Few (2-5) well defined and relatively unmixable classes, or 1 class that fights and maybe casts spells through items or difficult rituals but typically have no "race" distinctions (elves, dwarves, etc.).

The issue that I run into is that neither of these easily allows the kind of customization I'm looking to allow.  Even the Warrior vs. Mage dichotomy I'd proposed earlier seems like it complicates some things (why have a separate class for magic except in the name of "balance"?), and oversimplifies others (so your magical ability, based on class level helps you both to draw forth your natural physical strength, and prepare learn rote procedures better?).

So after more hemming and hawing, I'm leaning toward a single-class system (tip o' the hat to Bandits & Basilisks, Adventurers! Exploring the Unknown, and Into the Odd), but with a bunch of feats or feat-like-abilities which can be tacked on for customization.  Part of the idea is that a GM or the writer of a specific setting could chisel out portions of this universal "Adventurer" class to create individual races or narrower classes specific to a given setting:

Race - For races unlike humans, the character has feats and flaws specific to the race in question.  These feats come out of the character's starting feat allotment.  Any feats required for a race in excess of the initial feat allotment mean that the character pays experience costs for advancement as if they were one or more levels higher (i.e. equivalent character level (ECL)).

Class - In a typical game the Adventurer class is used and provides the following benefits:

Starting
Feats:  4
Skill advancements:  5 (no skill may have more than 3 advancements (+15 bonus) at this stage)
Saves:  Reflex, Fortitude, and Will saves are used.  Treat one save as "good" (4 + 1 per 2 levels) and two saves as "poor" (+1 per 3 levels).
Languages:  2 (any combination of written or spoken)
Weapons Proficiencies:  1 weapons group (+additional melee weapon groups determined by Strength bonus and additional light melee or ranged weapons determined by Dexterity bonus)

Advancement
Advancements are also taken at first level if applicable.
Attack/Dodge:  +1/level
Reserve points:  +3/level (add Constitution bonus every odd level).
Feats:  1 feat every even level
Skill advancements:  1/level

A character may trade in the Attack/Dodge bonus they would gain at any level for an extra feat if desired.
A character can not have a total number of reserve points less than zero.
The skill advancement system is to provide characters with some mandatory training and specialization outside of combat.  Optinally skill advancements may be exchanged for feats, but GMs are cautioned in allowing this as it may make for characters with narrower utility.

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For most spell-based magic this class system is intended to interface with a More Vancian! style magic system.  Psionics and innate powers will be based on abilities purchased with feats which consume reserves when employed.