I like the spirit of
Christopher Brandon's "Achtung Zombies" variant for M44[MS Word doc].
Summary: The German player swaps out his infantry units for
zombie units, made of the figures from the
Zombies!!! game. (Everyone seems to agree is a crappy game with fun figures, and as it happens they're on the same 1/72 scale at the M44 guys.) These units can
always move one hex or battle with a one-hex range during the German players' turn, regardless of the card played. They're harder to hit than normal infantry, and never retreat.
However, I don't want to even try the rules as he's written them, because they kind of don't make sense. They make reference to two different units not only sharing the same hex (which is impossible in the standard rules) but battling one another, and doesn't explain how that's supposed to work as far as dice-rolling goes.
More subtly, they interpret the figures within a unit as individual guys, and a unit losing figures explicitly as guys getting killed, which I think breaks the game. (Cuz then you
really have to wonder why units' battle strength doesn't suffer from attrition. The game's "damage system" is meant to be very abstract, like in the Civilization computer game, or even in D&D; the number of figures a unit has is basically its number of hit points. So long as it retains at least one figure, the unit is fully functional, but as the number of figures drops the unit is in ever-greater danger of going bye-bye through a successful enemy attack.)
My untested suggestions: Eliminate the knocked-down figures thing, on both sides. Zombie units simply ignore all flags rolled against them. The kicker: when an Allied unit of any kind is
destroyed (not just damaged) by zombie attack, the German player places a brand-new, three-figure zombie unit in the emptied hex.
He also doesn't mention how many battle dice zombie units get when they attack. I assume that he meant three, as per normal infantry close assault, but might actually suggest four, because: holy crap, zombies.