Parties

The Exile series limits the number of characters in a party to 6; the Avernum series limit is 4. The Lord of the Rings: Fellowship of the Ring is to me the key inspiration to the fantasy and the RPG genres. There are 9 characters in that party (and 15 in The Hobbit). Go figure.

Perhaps it would be possible not to limit the number of characters, although I'm not sure how a game engine would cope with this. If a limit were needed, perhaps 30 is a good one, being double what Tolkein needed.

Disposable characters and dynamic parties

In existing games people reload if one of their characters dies. This is partly because of the emphasis on character building and hence the amount of time that has been invested in that character.

In an alternate form of the game, characters will be dispensible and parties dynamic. The party that ends the overall quest may have none of the original members. Instead as members die, new ones are recruited from friendly towns and cities.

It may be necessary to recruit a particular character for a sub-quest, but ditch them when it is complete.

The obvious impact of this would be that character building would have to be scrapped. Characters would effectively be recruited pre-prepared with weapons, armour, items, skills, spells, etc.