I think it would be fun (assuming that it wouldn't make the game laggier) if more than 4 people could venture the clockworks/missions together in trade for having a higher elevator/revive cost, simply because it would be fun to have a larger diverse group of people.
- The price can be ridiculous to the point where the mission isn't profitable (remember the fact that we have mist energy).
- Every 4 revives, the price will double up.
- People would not have to wait for more others to join them when waiting inside of lobbies.
- Prestige missions probably shouldn't have this.
- Alts would not be an issue, since the price of using elevators would be somewhat higher ~15-20 mist/ce per person.
- The monster's health would stay the same or raised slightly higher.
tl;dr: Sometimes you can't get everyone you want to join you on a mission or clockworks run, so a 6-8 would deliver a much more fun experience if you're not grinding for CR. People can still do parties of 4 at the normal cost.
Story-line justification: Since the elevator is carrying more people, it costs more to transport them safely to the next depth.
No... just no.
Do you know that for every party member, all monsters get a health boost? 6 teammates would equal a crapload amount of smacking to beat one monster.