The relationship between Diabolico and Ryan
 

I would have liked to have seen more focus on the relationship between Ryan and Dobolico. Ryan seemed to be too well adjusted to the human world for someone that spent years with the demons. Other then having more knowledge about the demons, Ryan's relationship to Diabolico was dropped. I know the VA for Diabolico said something interesting at Morphicon 1. He thinks that Diabolocio viewed Ryan as a pet that needed to be put down ( once he betrayed the demons).

I don't remember much about Lightspeed Rescue. I didn't watch it that much. In regards to your other question: you might be right, I just don't know when or if they'd ever do that. I mean, they could put the Once a Ranger team back with these powers, or maybe the powers are never supposed to be used again. All I can say is that it would make for interesting fan fics.