First of all our wrenches are a joke, takes waayy to long to repair any vehicle.
second of all a tanker kit with internal repair wouldnt be instantly ofcourse.. it could take some time, you'd just be able to drive in to safety, or prepare a new assault, shoot etc..
I dont care about the lulz, but the wrench in BFH works pretty sweet. It will repair your tank - but over time - and if you get damaged during the repair process, the repair process is terminated. It means you still need to 'retreat' in to cover and wait for the heal, but you dont need to do a silly bail and whip out some universal magic wand and stroke your tank gently for a minute. :p The heal also doesnt bring you to full health, it gives you for example 100 HP and if a full tank has 180 HP, you need to be clever when to use it. You dont want to waste it unless you are actually below 80 HP (in that case you'll waste heal points) but you also dont want to gamble and go down to critical damage.
To me, that is more "tactics" then just press W and blow up, or take one hit and have to drive 2 minutes away, bail, wrench and get shot while wrenching, or waste minutes of game play for no reason.
naah, this stuff is old and arbitratry, we'd do good with some redesign in this department.