Class abilties strike me as the only one of the three that should see some increase in power every level (be it a bump to stats, more spells, weapon and non-weapon skills, etc.). Doesn't have to be the same boon every time/level, but somethng that is gained at every single level...maybe with "big" boosts (jumping into the next tier of spells AND getting extra skill slots/points/or however they're going to work those AND a bump to your primary Ability score, for example) every 3 or even 5 levels.
Themes, I'm not really clear on how these will work or could grow with the character. Would depend on what the theme is, I suppose. But, for simplicity's sake, I could see a progression like every other or every third level receiving some additional "trick of your trade" as it were (which I imagine will be reflected in something akin to being able to choose a new Skill, increase/improve "ranks"/fluency in an existing one or take/pick something "special" within your theme, akin to "Feats", a "Theme Feat" or somesuch).
The Racial bonuses are what get a little more complex...to my mind. If they do a break down of racial abilities that increase with level, I would think it need to be reflective of the race.
That is, halflings, for example, being not much more long lived than humans, perhaps gain a new (or increase an existing) racial bonus/skill/ability every other level. While the longer lived races, say Dwarves every 3rd level...maybe even going so far as every 5th for Elves...presuming they are the lognest lived PC race. I really have no idea what the capacities or life expectancies of things like Dragonborn or tieflings is...so presumably, they'd fit in there some place.
But, there, again, we then run into the old conundrum of "playing any race is better than playing humans" unles they come up with a bunch of, hopefully very minor, additional human "ability" tricks to go along with everyone else.
[EDIT] Or they could go mui simple and just have it be a rotating addition for "Class, Them, Race". That is.
At first level you start with your Class and Theme and Race abilities. At 2nd level, +something in Class. At 3rd level: +something in Class & Theme. At 4t level: +something in Class & Theme & Race. At 5th level: start over again, +something in Class only. 6th: Class & Theme, Etc...
So you're always getting something and every 4th level your gettign a big bag of goodies.
[/EDIT]
Dunno. Just think'in (or "typin'", rather) out loud.
--SD