It seems like what you want might be part of what WebRep does. Take a look at the newest beta where webrep is included. The users vote on different sites, but there’s also the Virus lab back end that does rating as well.
I don’t think we’ll ever have the option to “send this to the lab” because it would just be a lot of nonsensical scanning and wasted CPU cycles.
Think of it, if say 100 million users randomly send sites let’s say, 20 times a day just because they feel like it or want to know that a site is safe, that’s a LOT of scanning.
The way that they (Avast) sees it is that someone will get infected by a new virus (unfortunately). The virus will be sent to the labs, they’ll create a definition for it, and then everyone will be protected from that point on. Being involved with the avast community helps with detections as it sends files to avast that it hasn’t seen before, thus allowing them to find more infections and help it’s users better.
Yes, you could also use something like Norton DNS, but that’s if you trust Norton’s detections (which, honestly I don’t).