Breakthrough Tactics T4 seems a bit weak, especially when compared to Urban Survival Kit or Terror's Heavy Support. Maybe add something that could make Engies worthwhile front-line troops over Riflemen, like a massive HP buff.
If you pick Breakthrough Tactics then you will have Burnt Dirt which gives your crocs an aura that buffs infantry around it with Acc.
Also flamethrowers gain bonus range from Burnt Dirt.
More HP to the engineers.
In place of Top Gunners, maybe add a turn rate bonus or suppression or accuracy bonus for .50 cal gunners.
I added a turn rate and Surppression bonus for the 50. cals.