Tom,
If you take the leap and go for a Subscriber system similar to Twitch, you'll see high profile artists sign up to NG and bring their followers with them. For example, a subscription to "NG artist" would be $5. NG could take a cut of this, and give the rest to the NG artist. You could also keep the current Supporter system as well as adding this potential new system.
In regards to the $ and making sure it's all legal being the intermediary, as long as you follow the current laws (and hire someone who can deal with that) I believe it would be a worthy investment to research and implement.
PS: Thanks GoodL and littlbox for creating this great podcast for NG.
- Dimension Lord