If a player DCs, they should stay in the party, but to avoid being leeched, they will miss out on SP and Loot. Right now, that system isn't implemented. Main reason why I support their current system is because it can't be abused the way it was in FFXI. It possibly could be abuse, but the way it works right now would take chunks of time.

To the idea of keeping players within the party until they can log back on, well, imagine people force DCing just to chicken out of battles and claim loot. You can probably tell that I have a strong sense on how a community will be like and just how much they will abuse game mechanics just because they can.