There's already a couple programmable ignition choices out there for less than $300. I've got two different ones.
The one on my 200ES is programmable by a two button interface. It's a bit clunky to work and I always have to refer to the instructions to figure it out. I bought it used and it's been problem free for several years now. Works fine with the stock coil.
It functions without additional boxes on the 200ES because there's a 12vdc power supply and a coil powered ignition. For just a coil trigger it needs a box that rectifies and regulates 12vdc. The manufacturer sells those and I have one but haven't used it. For engines with only 12vdc and no AC ignition coil, it needs a box for that, which I also have but haven't used. I have the extra boxes in case I put it on something else.
The one on my dual sport bike is programmable via free software. It runs on 12vdc only but is triggered by the pulse coil. That manufacturer does sell ignitions for dirt bikes without 12vdc. I haven't used those.
I know the one on my bike has dual maps and I think the one on my 200ES does. They both have programmable rev limiters and can operate a dual or single fire, waste spark or not. The one on my trike has a built in, rudimentary, two digit tach and there's a tach output on the bike ignition. The trike one has some feature called 'pops and bangs' that supposed to do something goofy like make those exhaust farts. I don't know, don't care, and don't bother with that function. There's other features I'm probably forgetting.
Both are European made. Their websites may be difficult to understand with a translator and the instructions kinda the same, but both ignitions have been problem free.
I think someone here tried one of the MSD single cylinder ignitions and it didn't work out. Them, Holley, Accel, Mallory, any of that domestic stuff seems like junk anymore, likely because they're all owned by some large company who's office is filled with soft hands.
I have successfully run an ATC on a GM HEI module. The 185/200 engines with the mechanical advance can have the ignition run with all sorts of things.
As for FI on an ATC, I don't think, with the 250ES/SX as exception, have a robust enough charging system. Even then, it may have to be a low pressure system like TBI. Other than the ability of FI to constantly adjust (with enough sensors) to suit the conditions, I don't see a worthwhile benefit if the cost is too high. It's not going to add much/any power over a well tuned carb, but will add complexity and failure points. On new vehicles with FI, complexity and failure isn't really a issue, but on a retrofit...gotta make it idiot proof or it'll be a real headache for whoever sells them.
If you haven't already run across a small engine FI kit yet:
https://ecotrons.com/small_engine_fuel_injection_kit/