I really like the idea to make the two variants more diverse, good idea! Larger scatter in combination with increased range seems a fair trade-off.
The model does indeed have some garrison slots, but some them are on top of the roof which looks very silly. It is not possible to lock those while using only the others.

Maybe also up the dmg a bit, against light (unarmored) vehicles it seems a bit strange that a direct hit doesn't kill them, while a near hit also only scratches them - those shells aren't ordinary mortars, but serious bombs - not enough to penetrate armor, but to dmg them ;-)

i think the height difference is heigher between both (already more elevated) bunkers than between infantry mortar and motorized mortar - that's my justification for both suggestions about range - it just feels strange to put it down and get first line defences shot by mortars and need to take active action to reach them, thus the bunker could only defend itself automaticly, then i could also just place a few mobile mortars scatterd around instead building a bunker! ;-)

well, depends on where they exactly, if they have at least partially cover (the burried has sandbags on top) okay, if not yea sure, that would look rather weird xP
(then the model needs to be edited - but idk if that is even possible - i only text(mostly variables, i can read, but not write code without C&P) and partially texture (but only simple things - not an artist) mod - blender is my mortal enemy xD - some day i might face it... - but not exactly my life goal^^ - i just praise how ppl manage to use it :D)

But one of my goals is to get around how to make balancing stuff easyer, as i think it has some principles behind it i understand, but to bad at math to formulate them in a usable manner - but the insight that what makes a game interesting isn't a "matching"/fair balancing, but a diverse one, wich requires you to use units differently, but with tradeoffs that prevent them from getting OP in the overall picture of a game - making them superior in one situation, and inferior in another! - i think some of it can be automatically calculated, if you "model" the mathematical dependencies between them - like how much range coresponds to how large scatter, or dps as a famous example - you can easily keep weapons rather balanced if you keep them in the same dps range - one shoots faster but another does more damage - while in the extreme cases an lmg does lower dps than an automatic assault rifle, and a sniper rifle more dps, but because it isn't shooting at full speed it's "per timeframe" dmg is lower, and also that of the rifles, depending on the situation - i think there has to be a way to automatically adjust values depending on others! ;-)

Sorry for the long silence.
I finally looked into the values today and found that they already have different health stats. The buried version has 25% hp more (600 vs 750 hp). The other version has 2 more vets (okw) which provides 15% more accuracy and 25% faster rate of fire. After several tests, I think the current 115 barrage range is plenty and prefer to keep that the same for both for the ease of use.