I was short a player (had worked out why story-wise ahead of time) so we had 3, with 2 NPC's joining them - so yea, this would be a "smaller" group.
It was a blast and gave me an idea...
...I'm thinking that over time I could come up with some abilities that are tied to sets of PC's. Example...
An encounter power that is used by (requires) two players to spend their standard actions on, but does something really cool. So it could be the fighter and wizard saying "okay, on this turn we both use 'Burning Blade'"
In this (very basic) example, Burning Blade could do x[w] of the fighters type with an added bonus of x[w] from the wizards as fire damage, and perhaps a little extra (so as to be worth using this one as opposed to them each doing an individual attack). It could require them to be adjacent to each other, etc.
Or as another example...
"Flying Attack"
Say you have a halfling rogue and human fighter... they could have an encounter ability that lets the fighter toss the rogue 3 squares allowing the rogue to make (while in the air) a basic melee attack against each enemy in each of the two squares he flies over (if there are two - one if there is only one, etc). It would cost the fighter his standard action as well as the rogue's, but it would produce a cool effect that only these two people (pc's) could do.
I don't know, just an idea. I would imagine some would say that this is all possible via page 42 in the DMG and some creative thinking on the parts of the pc's - but I think working together with the PC's as a DM you could come up with some cool ideas and reasons for their existence within the story.
And also, they could still use the current method of initiative and delay in order to time it as required, but this 'new' method makes it much easier to visualize/control I think.