A dev guild could be interesting, why not.
For my part, I don't really need help on pts for my addons, but for some usage someone of an opposite faction could be useful, or a guild bank plenty of ressources, of huge tons of items to destroy, those kind of things. But we can need some help for exploring or other things.
Why not create "
Devs" on PTS?
The only problem is that because ZOS dump and erase the contents quite often, it could only be opened while PTS is newer than live. For my part I can provide HUGE resources for EU side (v14 chars, 2 full guildbanks, all craft maxed, lot of gold). but nothing on NA side except my level 5 char only created to keep my name for me
And for TS, if I can speak quite well english, a lot of devs here don't speak a lot english but only write
But why not.