Tracks get thrown, engines breakdown these are facts of life for armor crews you can try and prevent it from happening in the field but its going to happen. And as yet it still demands more then two hands and one brain to fix them even the most easily repaired tanks need more then one man.
As to the exo idea. You need more then just space. You need to be able to don it and doff it. In the open of the field or a base or on a naval ship that is one thing in the fighting compartment of a Tank space is beyond at a premium.
The most basic problems that can stop a tank are the track or a combination of terrain features that prevent maneuver. Throwing a track is a real issue and a tank crew is not going to always get that recovery vehicle for that or for simple routine maintenance. A crew has to be able to perform the basics on there own. That's what the Tank Biathlon was about proving who has the best tank crews who can load the tank magazines who can fix a.broken track and who can fix the very basics with out having to bring in a ARV to take the whole thing apart.
As we saw in the Russian victory Parade machines have problems that don't always need a recovery vehicle to fix.
A soldier in the field is responsible for the equipment he or she is issued and its basic upkeep and maintenance. From the carbine they are given to the tank they operate. The most basic level of repair and maintenance is always there responsibly. For a carbine if it gets dirty that means cleaning it if it breaks beyond what they can do then they turn it over to the armory. The same is true of a tank. Cleaning the tank, checking and changing the oil cleaning the gun loading it, fixing a thrown track these are the crews jobs. But if something really bad happens that's where the ARV comes in.
Now will there always be a need to have some one on watch during repairs? No sometimes there will be other units that can over watch but retracking a tanks is not a one man job, and you can't always be afforded the time to wait around for a ARV.