I just want to point out that micspamming happens outside of trading anyways, I reported someone to the forums for it before, but trading shouldn't be a huge deal.
Adding the !BP feature shouldn't be too hard, servers like DR have times where you die and have to wait for the rest of the round to do anything, so checking out someone's backpack and trading is something to do while they wait, and shouldn't be frowned upon. Spamming the chat and mic should be frowned upon, but not the trading itself. I don't know what we can do to prevent people from spamming, besides having a limit on number of times we can chat, there is already a 30 second on mic use.
The other issue I want to address is that trading on trading hell is about the worst thing ever. There are a lot of little kids, donators use it and their godmode ability to rank up stranges (I do this even) and some people are just in there to run around and kill people or micspam and not trade at all. Even worse some people only have low amounts of metal, so trying to sell high value items is a pain. Deathrun often has some loaded players, so trading on their might get your high value item sold faster.
Just thought I would share my two cents.