Edit: Thanks to all who answered my questions! It means a great deal to me!
Since the decision to bring back last names and also first names has become an actual effort (timing's irrelevant to me here), I've been in contact with a very close friend, who joined SL long before I did. I would like to, if the ToS even allows it (been a while since I skimmed it), sponsor a temporary (possibly even permanent) premium membership for her, to allow her to change her first name in-game and to receive a larger stipend than she does now (she got lucky and receives the L$100 legacy stipend).
My questions about the matter are:
Is it against the ToS to make such an arrangement, sponsoring two different users on a single payment method if all involved parties consent to it?
If she needs to downgrade to basic for any reason, will she lose her legacy stipend?
Anybody who can provide me with any answers will have my gratitude!