Is there any gotchas swapping out an electric interior for a manual one?

Dont particularly care about the electrics and may have found one in a preferred color which is manual

You can maybe swap the seat base and the backrest from the manual ones to your electric bases. At least the bases are easy, been there, done that. Backrest should be manageable as well. Very modular and compatible construction, like a construction kit for adults ;-)
The inflatable lumbar support might give You some work, IMHO worth doing, as well as the more adjustable seat base. At least for my ergonomics ... Yours might vary.

Heating has the same plugs either manual or electric.