I don't believe Sweden and Finland would be mixed together to suggest that Sweden did not represent itself as a civ, or that the focus of the civ was not Sweden. Sweden would just borrow some Finnish attribute akin to Denmark-Norway. Granted Denmark-Norway was a real political union, as opposed to Sweden-Finland, Finnish cavalry being utilised by the Swedish - during the time when Sweden held sovereignty over the area of Finland - is iconic enough that it would be plauseable to include them. This would likely be the closest Finland would get to being represented in civ, beyond Helsinki as a City-State, because Finland was for much of its history a dominion of either Sweden or Russia, and although its achievements against the Soviets are notable, was not a regional superpower in of itself - so if Sweden were not included, it is very unlikely Finland would be. And of course, if we're talking the fit of Sweden over Finland in this expansion, Sweden takes the cake. That doesn't mean Sweden would have any distinctly Finnish attributes - but its the best those who want Finland in the game can hope for.
Personally, I feel that Sweden already has two iconic possibilities for unique units: the Leather Cannon and the Carolean. However, from what we're heard, a lot of the new civs seem to be taking two unique units over one and a building/improvement, so I would rather that Sweden only have the one - which would be dependant, of course, on whether their leader is Gustav Adolphus or Karl.