My K4 is the only OT hilt I have that will likely be used in any capacity for Cosplay, Demos, general super happy lightsaber fun time (perhaps a Flex too), but those have already been staked out for single cell boards. MPP will mainly be a show piece, so I'm leaning towards the 16340 7.4v pack route and a nice Knight chassis.
I might pair up an ANH flex with the K4 for some Obi-Wan and Luke cosplay (Father and son). So probably have an ESB flex, MPP, and either a ROTJ V2 or Hero as the jewels of the collection.
And with SF going to release some new Apprentice hilts, looks like I'll need to pick up some new beaters!