That would be a nice addition, but I wouldn't say that it'd be a must-have function.
Still, a tiny bar somewhere in the GUI could provide the number of losses (say personnel, AFVs, guns and transport vehicles) say every 12 or 24 hrs. That would simulate the historical procedures, where Coy commanders would report the daily losses at the end of the day (or during the morning hrs of the next day) to their superiors.
Currently, to get the exact number, you can select all your units (zoom out, then hold down the left mouse button and use the rectangle selection marker to select all your units, you can hold down the CTRL key and do a left click on stragglers or units way outside the selection area, to add them to the selection).
The tab will then display the exact number of units AND the exact amount of troops, but also the total number of the remaining AFVs and guns. You then just have to deduct those total numbers from the total numbers present at scenario start. You can just click on the map boss to get that number (provided that all subunits are still attached to it) after the scenario has loaded.
You can also use this method to get an idea about enemy losses mid-game. Say you manage to surround British paras in Arnheim, then you select those enemy units to see how many troops are trapped inside. That info will be based on intel with varying accuracy levels, though, means it could will be based on a mix of vague reports, rough estimations and actual sightings, but it will give you a rough idea about the remaining enemy troop level.