It's a very impractical build, the only way to hit reliable with KE howitzers is to sneak up on people and hit them from behind. Difficult to do as a tank, and impossible in a one-on-one. But a UNAC on a team battle might be able to pull it off successfully. I don't think there are many people out there who can manually aim either HEAT howitzers or KE howitzers well enough to do more damage than they would do with a BR.
Worth a shot though, but I would be wary about taking it into any serious combat, since I see it mostly just uselessly trying to hit the enemy while getting out-ranged and out maneuvered the entire time, with extremely poor accuracy. There's just too many flaws to try and hit those possibilities.
Lol I've actually gotten more kills with h.e.a.t howies than any other weapon I've used, I'll say that if most players just put a couple sessions into using them they'd actually be halfway reliable with them. That being said everyone has good days and bad days and when using no lock weapons in these games on bad days, you REALLY feel it so my advice just don't let a couple bad first experiences kill the joy of these weapons for you.
As for the whole Ke howie tank thing I've used them a couple times with some great success actually you gotta be able to understand how to read your opponents though most people are predictable enough that you don't need to worry about having dead on aim just good enough aim for them to fly into your shots or splash damage radius