I used this doctrine extensively in the past and I moved on. I think the lack of tank kills it. I’d suggest:
0CP T34/85 (built at T4)
2CP Conscript tank hunter package (100 muni: 4 ptrs39s, camo, can plant light AT mines, grenade assault)
4CP TMDB heavy mines (70 muni: immobilises vehicle)
4CP Camouflage (AT guns and tanks can camouflage but must remain immobile)
9CP Mark Target
This is the best suggestion so far. Maybe add a few things to make it more worthwhile. I don't think the above would beat Guard Motor.
0CP T34/85 (built at T4)
2CP Conscript tank hunter package (100 muni: 4 ptrs39s, camo, can plant light AT mines, grenade assault) (maybe add building tank traps, as it would help make the mines more likely to be worthwhile)
4CP TMDB heavy mines (70 muni: immobilises vehicle) Camouflage (AT guns and tanks can camouflage but must remain immobile) (combine the mines and camo)
9CP Mark Target
12CP PTAB Bombing run (lower the cost to 140 to reflect current damage)
One other possibility would be to add Guards instead of the Bombing run. Guards and tank hunters work well together. The bombing run would probably be needed in 4v4's though.