The most important suggestion here I've been thinking of since Phase 3, is the addition of "Large" add-on variants originally from Paystar 5600TS to other trucks with longer frame, while I didn't address that feedback back then, now with Phase 4 I'd say it fits aswell.
The set of
Long Sideboard Bed,
Expanded Fuel Tank add-ons could be added to Pacific P12 and Azov 73-210, especially the first two that find new use with two 3-slot rocket cargo parts added in Phase 4, which so far only the Paystar 5600TS's add-on let alone can haul (without additional trailer). That addition may play well with the upgrade the Azov gets in Phase 4 already. The DAN 96320 could also benefit of its longer frame add-ons, yet its uniqueness requires additional model changes, which seems like an unnecessary hassle to bother.
While both flatbed and sideboard addons look and fit quite well with the said trucks, the fuel tank addition may bring some questions of the look (however several other base trucks suffer from the same issue of standard fuel tank add-on)
Seems like this small addition may improve a little those trucks in relation to Phase 4, given the small amount of work around (which is just reuse unmodified add-ons from Phase 3), I hope for consideration of it, since the ZiKZ 5368 just received similar upgrade of having now the TUZ exclusive Phase 1 add-ons.
While on the topic of "Large" variants, maybe it may be possible for the team to just spend a little time to make a longer variant of Phase 4's
Short Logs Carrier for Paystar 5600TS, Pacific P12 and Azov 73-210 to carry medium logs along this same feature of CAT 745C.
ZiKZ 5368 and colorable add-ons
Since the ZiKZ received an upgrade, the Phase 1 TUZ's add-ons are not longer exclusive to that one brand, maybe they could become colorable with one- or two-color scheme (especially since in Phase 1, their main color was heavily related to default color only of both TUZs), just like the Kung add-on happened in Phase 3.
While the Actaeon mudtires are equiped, they happen to pass through front fender upon steering.
The Small Maintainer Module fits well with the Metal Detector, yet the game by default doesn't allow to have then both installed, so far only with Small Sideboard Bed it is possible.
In the topic of colorable add-ons, the Loadstar 1700 Phase 2 skin still is only partially done on its add-ons.
Few other things
The Long Logs Rear Trailer is still missing a part connecting axle to the wheels.
The Sideboard add-on of Azov 4220 Antarctic, not really a bug, but its interest was brought to me so I thought I could mention it too, as it was left unused, seems like quite a finished addition, yet all it is now, is a bit of wasted resources for mesh and texture, I hope someone just forgot once to finish it and release.
Both Stages of Fuel Tank cargo have all their safe belts clipping through 3-slot sideboard bed.
Both CAT CT681 and Western Star 49X when equiped with Short Logs Carrier have their liftable axle wheel to clip through the said add-on.
Going through the files suggest that the CAT 745C Log Carrier supposed to carry also a Short Logs in Phase 4, yet that functionality is not in the game yet, either intentional or not.
After Phase 2 released, the CAT had ability to carry Workers Cabin, it was removed after Phase 3 release and being confirmed by Esorokin to be intentional. Whether or not it was mistake in first place, it gave the CAT a bit of unique use of having another exclusive cargo to haul (besides the base game container, which the cabin fits under container category as well), while the reason of removal wasn't given, I cannot think of any serious one to bother with removing it. So if there's no problem with having it in first place, I believe it will be welcome to add it back.