If the mech gets destroyed before you eject, your dead. Since it goes boom and you get turned into ash. If you eject out of a mech before it blows up, then you are just a BA that can walk around and shoot people. I do not understand any other possible circumstances where an ambulance would ever be needed. Nor will it ever be, as I have already said an APC does the job just fine.
The idea is probably that unless you are headshotted or the reactor goes critical, you might survive the destruction of your 'Mech. But instead of popping out of the wreckage as BA you would be in "wounded" state and unable to move (or could only move at a slow pace, weapons disabled) and you would have to be evacuated by the ambulance to a field hospital (the mainbase where you could repair your BA).
That said, there's probably a reason why no FPS or tactical shooter has this kind of gameplay mechanics. Granted, medi-kits or medic class does exist in more infantry-oriented games, but even that is taken care of by the auto-healing function of the BA itself, so they have no place in MWLL either.
The only situation where this would even remotely make sense would be a gamemode where you only have one "life", but even then, by the time you got into the "hospital" and back to the field, the match would be long over. Not to mention that you would have to find a player who would be a
dedicated APC/ambulance player, and assume that players wouldn't find creative ways to take out the ambulance without hurting their score.
