Because they have to follow the stack, yes, +5. However, focus items could do quite a lot (there's no limit, only how much power you can stack up).
Granted, that +5 ends up costing quite a bit of refresh: -7
15 points of refresh leads to +5 to power and +5 to control in one element. Add that to a potential Superb in both Discipline and Conviction (requiring 45 skill points). That gives you 10 power, 10 control.
Now, breaking things down a bit more:
Basic Wizard template is -7. That gives you four focus items and one point of specialization (for evocation, which is what I'm working with).
-15 points of refresh gives you 30 points of specialization. You only need 29 to max out specializations, so Billy says it's cool to have the last specialization grant one focus item and one point of specialization.
Now you're looking at Superb Discipline +5 offensive spirit control, +5 Spirit Control with Superb Conviction +5 Spirit power.
That gives you 15 offensive control, 10 defensive control, 10 power. At -22 refresh. With IoP shenanigans you look at -20.
I'd probably call anything approaching this at -10 refresh powergaming. Not necessarily bad (as you are sacrificing a lot of the side benefits that this character has, but still powergaming). As a GM, I'd probably question the character.
Lawbreaker gets you there much faster. Sponsored magic can get you there even faster. I imagine that many of the Senior Council might have sponsored magic of some sort (more like Kemmerlerian Necro than actual sponsored magic, granting "extra" specialization).
Also, they likely have stunts/powers that do things like allow faster casting of rituals (Turn Coat), other powers (Joe's shapeshifting/Blackstaff/Gatekeeper have all shown this). Possibly even longer endurance when casting spells (extra mental consequences?). It may even be possible to have the ability to cast multiple spells (Archive). I'd probably say that at one point, it becomes less of a numbers game and more of a tactics game.