Rashid has displayed playing around with Time... Perhaps he's more than just the Gatekeeper.
Perhaps. But I'd imagine they all have only so much space in their buckets. Harry's a warden, the Warden, and the Winter Knight. Rashid is a Senior Council Member and the Gatekeeper. The latter is a full time on-call job that wouldn't allow for much in the way of other demanding positions.
Are we saying that each SC seat has its own power boost. Or are we saying that each SC wizard may have their own things?
I think there's a WoJ that the Senior Council title doesn't come with a power boost. You have to have the power yourself, via blood or bargain, to even be realistically considered.
But I like the idea of seven roles of the original Merlin being divvied up to seven others on the Council, with the original intention of it being the seven Seniors, but over time it became less structured.
How I'd imagine it:
MERLIN [title]: Leader of the Council, with no power bonus, but plenty of authority. Langtry
ANCIENT [mantle]: Living repository of magical knowledge passed down only a couple times due to the bearers' extended lifespan. Mai
GATEKEEPER [object of power]: Eye-bearer in charge of the Gates. Rashid
WARDEN [mantle]: Authority over the Well. Also in charge of punishment for law-breakers. None, then Harry
BLACKSTAFF [object of power]: Bearer of Mother Winter's staff, Council assassin. McCoy
WAR LEADER [title]: In charge of the Council's war efforts. Petrovich, then Luccio, then Morgan.
CAPTAIN [title]: Captain of the Council's police force. Perhaps run by the WARDEN at some point, leading to an overlap in name convention. Luccio.
I imagine the structure would have been cleaner and more divided originally, but over a thousand years of politics an imperfect choices lead to changes.