ZylonBane

Intellivision games are sluggish because almost all of them use the EXEC, a 4K BIOS of common graphics/sound functions. Unfortunately, it only updates sprites every 1/20th second. The hardware supported 8 sprites, which could be reused vertically a la the 2600.

Playfield graphics for Grunts, missiles for humans, multiplexed players for everything else... yeah, it could be done.