I'm going to go with no on this one.
To begin, changing the squad sizes from 6 to 4 will do very little (if anything) to reduce stomping in Public Contracts. Four players (assuming competence) are very capable of stomping PUBs to the same difficulty (or lack thereof) as a squad of 6 players can.
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Then we also have the fact that one of the few strengths this game has over other FPSs is the ability to converse and enjoy the company of others. Being forced to play a PC or FW match just to play with your friends (without being forced to exclude some) will cause many to leave, as the social appeal is gone.
While one could say "that group should just play FW or PC", that is a flawed statement for a host of reasons:
1. Not all friends fight for the same faction, which means that the group will either be forced to exclude friends to play FW, group member(s) may be forced to betray their faction, or the group as a whole will not participate in FW.
2. Most squads play about 10 matches before disbanding, so if you don't already have clones (which only PC groups have), you will need to purchase clone packs (50mil ISK each). So if you want to play with your friends for the length of an average play session, you'll need to spend 500mil ISK.
Couple that with the logistics of forming teams, and the fact that all of these battles have to be scheduled 24hrs in advance and playing PC is an impossible solution to not being able to play with your friends unless your in a PC group (which the majority of players in support of this idea aren't in).
I like it, but the 18 man requirement will reduce performance.
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Moving on, in a balanced game, all roles are needed equally which means that each squad needs to have 1 of each-role to be proficient. With the current squad sizes, that's possible as we have 5 Infantry Roles (with one slot being open for a Vehicle Pilot). When all roles are needed equally, how does the inability for a squad to use all roles make sense?
You could just rely on another squad, but that's impossible in PUBs because the players there are usually terrible and can't be relied on for anything, and in PC (or FW) you can select the team composition and give them orders, making them actually reliable.
And while yes, many players have access to more than 1 role, the new players (the people that this change is designed to help) won't, which makes them unable to win a match as they won't be able to utilize all the roles needed to do so.
There are much better ways to solve this problem, and I personally believe that
my solution is better.