If you have a copy of Oriental Companion from RM2, I would suggest taking a look at it. If you don't have it, then visit the online store as it is available in PDF format [Dead Link Removed by Admin]
In it, there is this "blessing (a background option) called "Child of the Dragon King". It grants a number of powers/abilities (based on the Oriental Dragon though).
You could look at it, and maybe build something based on it.
It includes such things as
Immortality (i.e. like elves are immortal)
Damage Reduction
bonuses to physical stats
bonuses to RRs
recognition (i.e. other dragons recognize the kinship)
shapeshifting (chance to change shape, not an automatic thing)
Perhaps have such things as stat and RR bonuses be incremental (i.e. +1 per level or every other level or every third level).
The thing to do is to decide WHAT level you want the abilities to max out at, and then use that to determine the interval of the increments. For example, if you decide that 50th level is a good level to max out at, and you are giving a +25 to RRs and a +10 to all physical stats, then the RRs would get +1 every other level, and the stats would get +1 every 5 levels (if more than one stat, you could even spread it out across multiple levels (i.e. +1 St at lvl3, +1 Co @ lvl4, +1Ag @ lvl 5, +1Qu@lvl 6, +1 St @ lvl 8, etc..)
