This would be a terrible idea. As it stands already, AT/AA guns are massively vulnerable to tanks, planes and arty, and already take a good minute to repair as it is. And in that time, you can usually expect a plane or tank to return anyway, usually scoring an easy kill. And that's assuming an arty bombardment hasn't destroyed several guns/mg's/radios all at once... damage that would take a number of engineers many minutes to repair.
As it stands now, manning AT/AA guns is about the worst job in the game. You spend half your time repairing things (speaking of which, anyone ever seen anyone get more than 2 repair points?), and the other half generally being slaughtered by planes/tanks/arty. Why would you want to make it even more unbearable?
As Fuchs said, this applies more to some maps than others, and I could see leaving most light weapons(2 lbers, MGs, ect) as is. However, AA/AT guns are hardly that vulnerable on some maps, as any poor soul who has ever tried to take a solidly defended al Khad on el Alamien surely knows. And the thing is this wouldn't make it take any longer to repair guns or really make them any worse in most cases, it would just give attackers a window of time to move in after an artillery barrage or bombing on fortified flags rather than having the defenses become active again before they can even reach the flag zone.
And this would help defending infantry in a lot of cases too, since its difficult to mount a defense in areas where you're constantly getting raped by a flak cannon, such as the eastern flag on Aberdeen that is always get shot by the Flak38 at the middle flag. In that case even if you can convince a tanker to come kill the cannon it usually comes right back again almost immediately.