Yes this seems fine. I missed that also. I have to re-read that rule...
d20HeroSRD said:Permanent effects cannot have Alternate Effects, nor can they be Alternate Effects (since they can’t be turned on and off).
While true there is nothing by the rules to prevent a permanent power to become sustained duration at a net of +0 modifier.This is the line, under "Alternate Effect":
Anyway! I think the tentative plan that's taking shape is that we do a sweep of the museum for any clues we missed, then head back home to do some homework and debrief, yeah?