Like most, yes it would make the game realistic and could make you more competitive.
The downsides as I see it, is the advice offered (as hpurey points out), the time it would take to play with 3 others (would take up to 1 1/5 hours), people getting booted and returning to a lobby, and the sheer logistics of getting 4 in a group to play the same tourny at any given time. I struggle to get 4 players in Blitz some days, let alone players of equal ability/tier.
Seldom have I started a m/p stroke round with four and finished with 4 - infact only when I have played with friends.
I think the programming changes to set up separate lobbies for each tourny would far outweigh the advantage for WGT, personally I would rather see a new course added.