Fixed, long term bases generally have very hardened bunkers....eventually.
Forward operating bases usually just have holes in the ground (or high berms, or combination), dispersed around, and far from everything else, in which to store the nasty stuff.
This is a compromise of sorts, especially since few people actively hunt the convoys in the game.
Yeah, the ever-present porking Typhie can be annoying, but if we were running combat patrols and interceptors, and defending the bases at least half-way decently at times, those porkers would not be as successful as they are...especially against the small fields.
Any "fix" or "solution" would probably entail a whole rewrite of the damage
models or cannons would become ineffective against other targets, or increase the ammount of damage required to drop bunkers and troops.
Improvise, adapt and overcome.
