I remember now about you talking about that before. Does the Maruyama have recirculation? I don't believe the Solo does. I like the 4 stroke Kawi engine on the new Solos but I would prefer to have recirculation which is why I was looking at the ECHO.
As far as changing the plumbing on the Echo I think you are right. Much easier to just put a pressure regulator on the output. I didn't like that fixed orifice that Echo uses for the recirculation so my thought was to replace it with a pressure relief valve that opens at the set pressure sending the mix back into the tank. But the more I think about it I don't think the recirculation connection to the tank is large enough to dump the pressure. The test would be to just remove the orifice and see what the pressure goes down to while holding the handpiece open with tip you want to use.