A question about setting wide power modifiers

[Ulzgoroth]

While I wouldn't do it, one can 'zero out' an advantage or disadvantage that literally everyone in the setting has without too much disruption (it slightly messes with ally pricing).

However, that doesn't seem relevant to a limitation. You might have a limitation on all Sorcery abilities, but you don't have the same Limitation on skill ranks, basic character attributes, mundane advantages and disadvantages, and so forth. Do you? Thus the presence of the limitation does make a difference to character building. (It would anyway due to modifiers being additive rather than multiplicative.)

So just follow the rules. I'm not sure where double dipping would even be possible in this context.