no, it isnt.
Yes, it is. Nobody chooses who is on their side. The players are the ones who choose where they go.
most of the people who switch couldnt care less who wins a map or not, they just want to furball and get kills. there's a portion that just switch to run with whoever is hording at the time when they can switch.
There's also a portion of them who switch because all they see when they look at the map is green hordes not being defended against, but that doesn't fit into your scenario, so I guess you'll just be ignoring them.
side switchers are less likely to defend a base or attack one, to some this means nothing as they will easily switch and be on the other side and be the attackers, if it is convenient to them. they're less likely to resupply or bring bombers or goons unless trying to pad for "score".
I might be willing to concede the point that they'd be less likely to attack a base. Most side switchers are the ones defending a base though, it's a target rich environment. Also, are you saying if those players didn't switch sides, they'd be constantly resupplying and running goons? I think not. To some, virtual delivery truck and bus driver is not fun. I'm sorry that doesn't fit into your plans to have other people run goons and supplies to keep you able to fight and do what you want.
what holds the game together are those who dont switch or squads that will stay in one country for a month. they're the ones who create these fights when attacking other bases. side switchers just take advantage of them.
By defending bases, because nobody else defends. Win the war types are only ever on the offensive, because taking ground faster than the other sides is by far the best way to win the war.
side switchers are only good for a few things in the game: the constant whines about how they cant switch due to the time limit. and the lack of "good fights", meaning they want something started for them instead of creating it themselves. and another "I switch to balance the sides" bs they're usually talking about.
to these side switchers whiners I say 
semp
And to the entire chesspiece underoo brigade, I also say

You're the problem, and you don't even realize it.
Wiley.