So, I'd like to suggest an optional guild rank that a GM can elect to use. If Blizzard would enact an optional council-type rank, this council could govern things like GM ownership. For instance, if the guild was sold, the GM could try to use the 'promote to Guildmaster' option to give the guild to the new owner and those who held the council rank would have a dialogue box ( maybe something like the /kick box in DF/RF) that read 'would you like to promote so-an-so to Guildmaster?' and they would vote yes or no. A system like this could not only save a lot of guild drama, (not to mention open tickets) but if such a system were available, GMs couldn't pass the guild off on a whim, and those that felt a sense of entitlement would either have the vote to validate it, or not – either way, guildies would know where they stood in terms of guild control and their voice's importance in it.
Again, if you kept this rank optional, a GM could elect to give no one else in their guild that kind of control and thus, would be sole owner and if they chose to sell their guild, guildies might be a bit more understanding of it.