That certainly makes sense, both from a rules perspective and flavor-wise (how much maneuvering is going to be possible when charging in formation?) Kings of War used a combination of that 90 degree max pivot with "arcs" (e.g. front arc, side arc, rear arc), where whatever arc of the enemy unit your unit started in was the arc you had to charge. In fact, if I recall correctly, I do not think you got to make a 90 degree pivot while charging; rather, you had to charge the enemy's side that you started in, and then you "aligned" yourself to that side, once you made contact with any part of their unit. Does that "aligning" make sense?
I like my tea, as I like my nights: dark, endless, and impossible through which to sleep.
In our group, we initiated a simple 'arc' restriction as well. You could only charge whichever arc you began the activation in. This solved the problem for us because we had units shift to match up as best as possible after making contact and didn't enforce any restriction on fighting models. If you charge, everyone in the front 2 rows fights of the charging unit fights (same for the defenders if they're hit in the front). If we use arcs but still allow the pivot, a simple pivot during the move could prevent small chaff from blocking bigger ones by being positioned oddly.