I think a distinction needs to be made between "channeling the Weave" and "receiving a divine favour". Clerics draw their power from an entirely different source to what mages do; evaluating them on the same terms seems a tad mistaken.
As for devas and planetars, I'm almost ready to agree with you... Except that liches have even less interest in being controlled than the current high-level summons do. When Jaheira gates one of the elemental princes in to do my fighting for me, I don't find myself imagining that they couldn't turn on me if they wanted. I think of liches more along the lines of pit fiends, in that they are single-minded and totally unconcerned with their summoner's desires. For the pit fiend, nothing is more important than fighting the Blood War, although if that's not on offer they'll settle for killing whatever looks like a worthy opponent; for the lich, nothing is more important than achieving more and more power, and they only fight if they have to, if someone is getting in their way, and I'd think that anyone stupid enough to summon a lich would be the first on its mail-bomb list.