I don't know if it's been suggested (if so I'm all for it!) but I had the simple idea for having advanced and monstrous races available for play at 1st level; tie the acquisition of some of their more powerful abilities to trait and feat expenditures. For example a generic "advanced race" trait available at character creation could grant a character +2 rp; ideal for playing 12 rp races such as aasimar and tieflings.
In turn, further racial advanced and monstrous abilities could be acquired as the character advances in class levels via stackable "improved race" feats; each of which would grant +4 rp worth of enhancements each.
So, as a PC-friendly option, advanced and monstrous races would have some of their more powerful racial abilities listed as being acquired via feats, perhaps with prerequisites for added balance. This could represent, amongst other things, a young member of an advanced or monstrous species slowly maturing.
For example, imagine a dragonkin themed monstrous race with some of its racial traits being listed thus:
ADVANCEMENTS
Claws: A dragonkin grows claws capable of dealing 1d6 damage each via the improved race feat. Prerequisite: Character level 3.
Wings: A dragonkin's wings finally grow strong enough to allow him to fly at a speed equal to his base speed (average maneuverability) via the improved race feat. Prerequisite: claws, Character level 5.
Breath Weapon: A dragonkin develops the ability to breathe fire for 1d6 damage per character level in a 30-ft. cone once per day. Prerequisite: claws, wings, character level 9. Special: This racial advancement may be selected more than once; each additional feat allows the dragonkin to use his breath weapon 1 additional time per day.
Please, don't forget this feat!