What are the options for a drop out turned professional to return to academia?
I was in a similar situation about a decade ago. I just went ahead and got the BS degree. I was a systems admin for about 10 years prior. Here are my thoughts:

Of all the classes I only learned useful stuff from about 4 of them. Data structures, algorithms, signal processing (ironically in a brain device class where the equipment was garbage), and operating systems. Everything else was a complete waste of time including all the calculus' (more than 2 years worth of calc+ math)  and general ed.

Id say that if you already know algorithms and data structures real well along with memory management and signal processing then there is no point to either a BS or MS degree. You will learn nothing. But if you have not seen those subjects before, it might be worth it though I suppose, now that I fleshed out the entire thing for you, you could just get a few books (lol). By the way, I teach CS now at both undergrad and masters level even though I dont have a masters. That said...

I actually started a MS degree once and all I got was the same education but more specific to certain fields like signal processing sound waves for voice recognition. I learned nothing in that course but it did require a huge amount of my time which I didnt want to waste on such a trivial thing that I can figure out without instruction. I just dropped the program after that. If you want to go into education however, you really should get a masters which is the only reason I am currently considering doing an online program. But if youre already in the real world, id say time is better spent making a product.