Hawk Atari BASIC guy from way back in the day, too 🙂 Just in case you've never used it, Fast Basic by dmsc, for the Atari 8 bit machines, it heads and shoulders above other Atari BASICs. It wipes the floor, speed wise, with TBXL. It even trades blows with Advan BASIC on lots of things.
I recall seeing register and memory info for the video chip used in the original BASIC Engine, but not in the NG iteration. It would be neat to do some scrolling by just hitting a couple of registers. The next thing on my plate for the NG was to learn to use PLOT MAP correctly. I look forward to see what you come up with!