I am for the following:
1) adding a few extra base classes (e.g., a PC aristocrat or Courtier, the swashbuckler, an OA shaman, a more traditional shaman (preferably like that in GR's Shaman's Handbook, but the Spirit Shaman will do) and a battle sorceror type class)
2) adding several examples of variant classes (e.g. cloistered cleric, the wilderness rogue, urban ranger, barbarian hunter, the monk variants, and the thug variant of the fighter) as examples of how to tailor the classes. The combination of classes and variants provide numerous options that can represent cultural or environmental variants that characters should be able to play at the start and also help the DM shape the cultural and environmental aspects of his campaign .
3) Keeping feats, perhaps eliminating some or many
Now, I know a lot of people say variant classes are too close to 2e kits and then knock the 2e kits. In my opinion, 2e kits were a good idea too often done with poor execution. The idea behind the the kits of fine tuning standard classes to fit standard variations was good. The problem I think was due to 2e mechanics which were weak in comparison to 3.X . 2e lacked 3.X streamlined and integrated mechanics as well as additional features (e.g. feats). The result was the kit designers created goofy mechanics (e.g., the fighter kit with bonus that was the character acted " as if under an alarm spell" ) to patch a hole in the rules or they often created unbalanced kits (there were probably some other reasons as well for the latter).
That said I thnk some of the 2e kits worked very well. I definitely liked the Complete Thief's and Complete Druid's Handbooks kits and all. So, I think the concept can be done well and I think that the 3.x mechanics when combined with the addition of a few additional base classes would be a good start in helping the players find a better concept fit for thier characters and variants would help tailor the character further (while improving multiclassing by giving the character more abliity to stay on focus with concept). for example
Aristocrat: Courtiers, Nobles, Merchants. Focus on Leadership, social interaction abilities and the ability to use influence to call in favors. Variants would include for a more martial or roguish aristocrat (including spies). Another variant might work for a non-spellcasting bard.
Barbarian: a warrior figting with rage or passion. Variants can include the Barbarian Hunter from UA, or an Urban Barbarian (make a few modiifications incluidng swap out skills similar to the rogue/wilderness rogue or Ranger/Urban ranger).
Bard: personally I would like to see this as a master of lore, social interaction, with enchanting performance (music, singing, oratory, or storytelling) rather than the jack of all trades. Spells would be focused on Charm and Illusion with additional modification determined by the variant type (e.g, arcane sage, divine bard, or rogue). Variants might include the Arcane Sage (gets additional arcane spells) , Divine Bard (addition of curing and priestly spells), Roguish Bard (only spells focused on charm, trickery, illusion ,but more skill focused)
Battle Sorceror: for characters equally focused on arcane casting spells and martial capability
Cleric: Returns to the idea of previous additions of teh Cleric being a Martial Priests serving a deity. It is the warrior/priest class (for non warrior priests, see the priest below). Variant includes the include Champion of good from UA
Druid: Personally, I think the druid coud be as priest or shaman with the right domains (see both Priest and Shaman below). The priest and Shaman are more broad archetypes.
Fighter: warriors relying soley on martial prowess. For a fighter with a more skill focused background you could use the Thug from the PHB as a guideline. By switching some skills you could get numerous variants including an ex hunter, an ex mariner. The character could also trade medium armor for another concept related feat.
Monk: nonspellcasting martial artist. Variants including the steadfast monk, warrior monk et.
Paladin: I think returning the cleric to the religous spellcasting warrior would rmakes the Paladin superflous. For Joan of Arc type characters and other characters with blessed abilities, who do not cast spells, I could see creating a True Faith feat tree. The True faith feat tree would be for representing non-divine spellcaster who are blessed with abilities. Feats in the might include the ability to turn undead (which keeps with literature and film of any faithful truly faithful christian or catholic being able to turn a vampire) Divine Strength. some kind of Augury ability (hearing the voice of god), etc.
Priest: non martial priests serving a diety. Variant Cloistered CLeric
Ranger: I can see the ranger remaining as an archetype of a warrior/spellcaster. However to do so , I think spells should begin much earlier so it is more of an equal emphasis on warrior/spellcaster (not getting spells until later makes me feel a prestige class is more approriate) . More martial focused could multiclass with barbarian or a wilderness fighter variant. while a desire to forcus more on skills at a given time could be done by multi class with wilderness rogue variant.
Rogue: Focused on stealth. By choosing a wilderness or urban you can better choose the type of focus of your character. There should be more options to be substituted for sneak attack at various levels so characters could have some sneak attack or none at all based upon concept
Shaman, OA: martial arts spell casting priest. variants would be by type of spells (i.e., shaman oriented, divine oriented, or arcane oriented)
Shaman: spell casters dealing with spirits (e.g., ancenstral, totem, etc.) rather than deities
Swashbuckler: a lightly armored fighter with a bit of roguish flair.
Sorceror: innate arcane spell casters
Wizards: Scholarly arcane spellcasters
Specialist Wizards: Personally, I would like to see the UA variants abilities standard. I would also like to see a return to Specialists having their own lists.