Thats a moot point, if you own the majority of nodes in any system you can do whatever you like.
No it isn't. This is a critical difference between POW and all other designs; owning a majority of POW hashing power gives you the ability to attack the network, *but* you have to expend energy to actually do it, and that changes everything.
Therefore if you want to vote on the outcome of a conflict, you MUST of done work and been endorsed recently. Historic weight with this change is no longer a factor, so the long term con as you put it is gone.
What does it cost my majority of nodes, then?