(this should probably be posted on a 'variants' forum, but I suppose rules questions is close enough)

Has anyone tried simultaneous phases rather than players taking turns sequentially?
If not, how are you balancing the first player penalty?

simultaneous? never tried that

What Ive tried with multiplayer is

4 players... 2 teams, with alternating turns. PLayers 1 and 3 on one team and players 2 and 4 on team 2

To balance regarding first player penalty... every player but the last player gets the first turn penalty.

With 3 or 5 players... teams dont work, so we played with a resource penalty to attack a player who was already attacked this turn.
Basically, the first player to attack a specific player attacked for free, if a second player wanted to attack that previously attacked player, then you had to pay 1 resource. If the third player still wanted to gang up on the same player, he paid 2 resources. This prevented ganging up.

Victory conditions... either burn 3 territories or last man standing... First option prevents player elimination but encourages ganging up.