yea I have been off of Verizon service for long time now(almost a year)
what I do is Google on airplane mode. then you can just turn on wifi(bluetooth.and wifi are able to be toggled on/off without affecting airplane mode)
I get actually good battery life on this thing that way lmao!
but yea, you can always change your setup later by just using wifi to download your Roms/kernels.
not having service won't affect ability to install roms.
but make sure you do toggle airplane mode on lol. cuz without service(i don't even have sim in anymore) it will be constantly trying to connect to a tower to get a signal, and will horribly drain your battery very fast.
(I've also removed BIP.apk and the stock messaging apk since they always show as running apps and I don't need them anymore I figured just remove them to free that ram up. you will have to remove them every time you flash a Rom though remember, if you decide to go this route as well)