I have most of the Vanguard upgrades now and have decided to have a go at the Engineers Utility Pouch.
After watching Scriv's video I decided I just needed those extra mines
I have now unlocked the third stage , giving me two extra C4 and one tank mine.
I have died more not having the Flak Armor, but it will be worth it if more kills are achieved with the extra explosives.
It will be expensive to max out, but hopefully worth it.
The cost:
200 Certs for 1 extra C4
400 Tank Mine
500 Another C4
1000 Another Tank Mine
1000 1 extra Proximity Mine
This will enable a max of:
5 Tank Mines or 4 C4 or 3 Betties.