[Sidecutter]

Actually, it seems pretty ironic that the OLDER riders act as powerups for the newer riders. Considering that every crossover movie between the prior series and the following is predicated on the idea that a monster from the new 'verse is so powerful that the rider from the previous universe, usually with every powerup ability he gained during the entire series, gets his ass handed to him by an everyday "normal" monster worse than the biggest baddies in his own verse did.

And then the new rider walks up and kills the monster like it was nothing. By implication, every rider is markedly more powerful than the last. So at some point, an old rider would be like being slapped by a newborn baby, in terms of power against the current monsters.