Not sure what installing Vanguard has to do with combatting smurfs, inters and ban-dodgers (because thats the main issue and installing vanguard wont have any effect on that) but everything else looks alright.
Doubling the duration of arena matches is a bit of an ick for me though
Vanguard - one of the big issues right now is the number of accounts that get levelled with bots, creating a range of relatively disposable accounts that a certain type of player will then use without care for how they affect others, whether their account gets banned or restricted etc. Vanguard should let us rapidly detect and ban said accounts, hence the improvements to smurfs/inters/ban dodgers.
Arena - Doubling teams won't double duration, agree that Arena doesn't need to be a dramatically longer mode. For most teams it'll be about the same length, if you're in the final two it will likely run a little bit longer. Regardless of the number of teams present though each round half of the teams in game are going to be losing health, so elimination will mainly happen at the same pace