Great stuff. Looks and plays really well I'd probably just add some manpower cost to all trenches (if there isn't any in Ur mod) in order not to spam them too mindlessly.
That's actually how trenches are for the Osttruppen Doctrine in live. I think as well as the community defensive doctrine and OKW heavy fortifications.
None of the current trenches available to any of the commanders or factions have any cost associated with them. Unless you mean a mod you've created and have a "live" version for.
In regards to the thread suggestions:
The changes to the panzerwerfer are very interesting and I particularly like the smoke barrage idea.
I don't like the recovery squads idea. I get that its a throwback to CoH 1, but currently there are no abilities which positively augment manpower income in anyway and this is for a good reason. It will have drastic effects on factions or build timings that are manpower tight and still have potent effects on ones that aren't.
I like the idea of adding suppression to the railway artillery, but I dislike having all the shots arrive at once. The suppression helps with area denial, but the alpha strike damage instead of consecutive shots negates it.
Garrisoning mortars in trenches is a cool idea, however I don't like the range increase or especially passive healing. If trenches were given a SUBSTANTIAL mp cost like say 100mp, then perhaps passive healing could be ok but if they cost only 50 mp(like the old trenches) or if they were free as now, I feel like players would just build 3-4 trenches in base and skip the bunker medics or equivalent. The micro tax would be higher but healing overall would be faster due to more models healing, and the resource cost would be lower. I feel the barrage range just rewards putting mortars in trenches too much, you already get the durability increase against enemy indirect fire, adding additional range is too much I think.