hmmm I do like the idea but
First someone mentioned put it in guild bio,,, that works great till someone complains and its removed because listing guild names is against ToS (or thats what the person in question was told when their guild bio was removed for having another guild listed that way)
I dunno about "flip a switch" id like to see many parts of this added with the idea including something on the players bio listing them in big bold hard to miss and near the attack button "this is a guild ally!"
And a way to buff all guild and guild allys that are online would be fun
Id have to ask how much will each ally or enemy cost a guild? This will be a big factor on if I support it
And sadly this was needed years ago and really not so much nowdays so perhaps it wont find any priority now