Custom constrain angles, isometric Pen tool

I've read a couple similar posts on this subject, but I havn't seen any that specifically requests for a feature to be added.

The base questions: Why can't you set up custom constraint angles like you can custom construction angles? Why do the line segment tool and pen tool behave differently when I change my constraint angle?

When I set my constrain angle to 30 deg. holding down shift, the line segment tool snaps to 0, 30, 60 ,90, etc. but when using the pen tool snaps to 30, 75, 120. Reading online, people want them to behave the same but some want 30, 75, 120 and some want 0, 30, 60, 90.

I do technical drawings for work and I draw in isometric 100% of the time. I make dashed lines to indicate how one part goes into another part. I use the pen tool to generate those lines. It would be awesome if I could hold down shift and have it constrain to 0, 30, 90, 150 (straight up, straight across, or on the iso plane). None of the plug-ins seem to do this anywhere near as efficient as simply holding down shift, or (what I do) keeping a grid in the background to follow.

My searching online lead me to the conclusion that LOTS of people want varying iterations of what I'm getting at here. So why not make it customizable? The construction guides dont quite do it.