What would be the benefit of this tho?
You would not get the same item (so you would not do it for equipment).
You would not have the same fight (so you would not need to use the same strategy or have same experience).

Sounds like it would end up being a different quest all together, just recycling scenery/monster.

If it is a 'little reward' then could the same not be accomplished by doing a totally different quest that gave a little reward for solo-4 players?

Or am I missing what you are trying to suggest?