I hate to bring this argument up yet again, but if I were to try to create a free sprite class, has anyone had any luck in basing it off of an AI or a free spirit, and them modifying it to suit? On the one hand, their Matrix limitations suggest an AI base, but the lack of a home node suggests a free spirit.

If neither modified class works, does anyone have a completely novel method of creating free sprite characters? It seems like the concept is playable, but I'm not sure how to make the numbers agree...

I'd go for free spirit personally. Sprites have always seemed way too much like spirits to me.

Free spirits have the list of powers and costs on page 92 of Runner's Companion which you'd have to compare to all the sprite powers and make a list for all the costs.

On the other hand, trying to make rules for free sprites by basing them off free spirits will be a nightmare unless you just use A.I. stuff and pretend, so it can get a little crazy.