Simple idea really.

Don't loose the set that someone has sent you when they/you go to spectate or pit etc.

It would be better if you could receive a set at any time. At the moment you have to be in pits or race and so do they. If either of you go to spectate or a new race starts etc you loose the set they sent and have to ask for it again. I'm assuming this is because the set isn't actually sent until you get to the "save" point.
It would be better if the set were actually sent to your pc and automatically saved with their name at the time they send it to you. Then when you go to the pit you will find it there whatever happens "in game", at which time you can rename it as you please. I don't really see the purpose of having to manually "pick up" sets that have been sent.

Another way of doing it might be to have a "request setup" (RS) next to the driver name on the connections list. This will pop up a request on their screen telling them who's reqesting and they can choose to send, deny. This will pop up text on the requesters screen saying "<driver> denied request" or "setup received from <driver>"

+1 for the ability to send and receive them while spectating

~1 for requesting, maybe only if the pop-up box appeared after the person has finished.

I wouldn't like everyones setup requests spamming me or popping up. It's bad enough you can SS to everyone and spam them now, but isn't so much of a problem atm because you can't beg someone for something you WANT by sending a setup. It's bad enough when people beg for setups and wont shut up about it in the chat. Imagine the temptation from noobs to spam requests for sets to individuals? That would annoy me more that the inability to save sets when the sender has spectated/pitted/left server.

Simple thing I think is just to "S"ave the setup as soon as it's sent. If you already asked for it, you should be prepared to save it as soon as they send it. I'm pretty sure if you click "S" before they actually pit then you still can save it, even if they pit while you are typing the filename to file it under.

oh well my 2cents.

+1 for sending while pitted. Absolutely

Not sure about a request system though. As long as it didn't spam the person with text or windows it could be alright. Maybe if it told you when the request was sent and maybe again when you stop or something it could be okay. And a little section on the Connections list next to the Send button could light up to let you know who wants it.

Ok fair points the request system is open to abuse, I had thought of that but I thought I'd throw it open for debate anyway.

Of course if you ask for a set you should be ready to save it, but the problem is timing. Even if you're prepared, you have no control over whether the other person spectates or disconnects immediately or maybe the race starts and then you loose the set that was sent.
Even if you are sitting there waiting for it, as has been said already you may not get one so you're sitting there staring at the text waiting for a "sent setup" message that may never appear.

I still think the best solution is an auto save system where the set is actually sent when the text says it is and is automatically saved. I don't see the point of making things less user freindly when there is a way of preventing it being so with no negative impact.

+1. It would be great if you could send sets from the Pit screen. Though it could be a nice update, some stupid people might simply abuse it. Example. Let's say you're in a long race in a public server. Then someone came in. He spams pressing SS to everyone racing. It could cause distraction. Good idea tho'.