Hi LRM! Are you new to FMQ ? If so, and you're able to FMQ on your Class 15 clone, you could start with that machine, and do smaller projects: table runners, place mats.
I started FMQ on a Singer 411G. The throat space was small, but I did quite a few small projects. Like your Class 15 clone, my Singer had no "needle down", speed control or thread cutter. So quite a few "cons" ... However it was good practice, and didn't cost me a cent LOL
After a while, I wanted to do larger projects, and purchased the Juki TL2010Q about 5 years ago. I can find no "cons" for that machine. I did a lot of research before buying, and bought online. No regrets whatsoever.
So if you can FMQ on your Class 15 clone, and are satisfied with the results, you could stick with it until the time comes when you're no longer happy with its limitations.
Keep us posted.