I will definitely have to do one or the other local build and for that native is still best (for this particular snap). while I can cross-build the vc4 libs and omxplayer pretty easily, the snap also builds ffmpeg (to link against vc4) which has a lot of build dependencies … while it might be possible to cross build it with jumping through a lot of hoops, i have not tried that …
i do my initial builds on an old sabrelite board i have lying around and simply go for a coffee when it builds 
but once i have a building snap i simply leave all the building to https://build.snapcraft.io, do my changes in github and use the edge channel as testing ground.