Mean Streak didn't hold up because of its design, not because of the weather. I think that it says enough that several Dinn-designed coasters, including Mean Streak, have been converted to RMC. Of 11 coasters built between 1988 and 1991 by Dinn, four have been removed, four are still operating, and three have been converted to RMC.
IG should be fine. I'm not an engineer or construction specialist but they didn't build this thing to collapse anytime soon. Seems to me, the biggest thing will be getting the sensors and items like that working smoothly, if they haven't already.