For now, I am going to assume a 4" square grid1 and use FOW as the basis for a number of basic stats. The first problem is that distances in FOW tend to be in 4" increments, except for most notably infantry movement! That is okay, because I have never been keen on infantry moving the same distance over open ground as through cover, so the basic infantry move will be 2 squares in the open and 1 through difficult terrain. The basic infantry combat range will be 4 squares.
One abstract concept where M44 and FOW differ is in the decrease of combat power over range. With infantry in FOW your combat power is the same throughout your single range band, unless you have a heavy weapon, like a mortar or an HMG. For now I am simply going to use a single range band with a single combat power for it. As there seems to be no reason to not use the FOW numbers, infantry small arms range will be four squares.
Another FOW concept that I like is the use of ROF to indicate the number of dice to be thrown. Again, at this point there is no reason to not use the same values as in FOW. Thus, rifles will have one die, rifles and one MG will have two dice, and rifles with two MGs or SMGs will have three dice. As with FOW I like the concept of more experienced troops being harder to hit, but like TOI I prefer the defender actually roll dice for their defense. The basic TOI combat mechanism is for the attacker to roll their dice looking for hits, and for the defender to roll their dice looking for saves. Saves subtracts from hits and any excess hits go towards damaging the defender. As I do not like the TOI mechanism of either hitting to kill or to suppress, but rather prefer the FOW mechanism of pinning if enough hits are achieved, the combat results have to reflect this increased chance to save against kills.
The question then becomes what is the basic chance to hit an infantry stand? In FOW the chance to hit conscripts are 2+, trained on 3+, and veterans on 4+. Of course, this is often modified by concealment and going to ground, both of which typically require markers on the table for infantry2. This will require a bit of pondering. My desire is to have both sides roll dice, either in an opposed roll fashion, or as hits and saves. I don't really want to reduce it down to a single die roll.
1 I could use an offset square grid, which allows you to simulate a hex grid, but will keep it as a simple square grid as is easier to show in the table.2 I try to eliminate markers from my designs. I do not usually succeed, but by starting with the idea of not using markers it usually puts you in the proper mindset so you end up reducing the number of them.