As a frequent buyer and seller I'm personally not very interested in most of those changes, although I'd be fine with them if the community decides they're mandatory.
- External Feedback - I think this is something that is great to add if you have it, but should not be mandatory. For the regulars here I think their local reputation is more valuable and for new members I wouldn't exclude a seller just because they haven't used those other sites. You have to start somewhere.
- Timestamps - As mentioned earlier in this thread scammers can either fake these timestamps or take pictures of real items and just not send them. As a buyer I've never asked for this or care too much if a post has them. As a seller I am happy to do this if a buyer asks for it, but I usually won't go to the effort unless asked.
- Prices in listings - I'm all for keeping the prices in the sale thread as I like to refer to them as a source of market trends, especially when preparing my own sales. As for listing the agreed price and who purchased it I'm not sure I think it's reasonable to compel people to do this. Listing agreed prices ends up negotiating against yourself if you have multiple items. I don't think we've seen much or any of the selling a single item multiple times here yet.
As
@T_Minus pointed out it's up to each seller and buyer to determine the effort they're willing to put into reducing risk and how much risk they find acceptable. If the transaction isn't leaving you comfortable it's best to politely walk away.