This new system with no caps seems good, but without a true stopping point some players can get considerably above others even with the large exp requirements. I know Berlin is going to be getting rid of RB passives soon, so that will fit into this idea well.
Level 150 cap RB
Lvl 140 cap just seems so random so make it 150.
Alright now here's the deal...
1. The experience required during this will be a considerable amount throughout, so much that most people will want to save up a lot experience in their 3rd RB just to RB.
2. Upon RBing, instead of a RB passive you get something called Overcap Points. Judging by the fact that you get +30 levels, you should get +30 overcap points.
3. Anytime you overcap a stat passed its cap you lose 1 overcap point.(Counting RB caps, so if you had +10 speed, you wouldn't lose an overcap points until 41 speed.)
4. When you overcap a stat using an overcap stat you would not gain a level, you will just spend one of those points, so 150 is not just a RB to overcap nin to 65. It's a way to get an Uchiha to 50 ninjutsu while still having 30 tai and 20 strength on the side.
5. This is where it gets interesting, because some people may go pure nin and others may try to overcap stamina or go balanced. Allowing much more build diversity than there is now.
In the end it will still require a very long time to reach lvl 150, particularly when you get to 30 in particular stats, so people should probably stack up tons of experience during level 120 to avoid the grind.
Level 120 is where the average prodigies lie, level 150 is where the Gods like Madara and Hirashima rank.