I did mention the microtransactions cons point.
Regarding the green and red bar - it can be implemented at the client side ensuring that there exists this address on which you want to sell. But after hearing to this type of malware, I think the idea which I proposed would be really safe.
How my idea works :-
With every Address there is a keyword associated which remains constant forever.
So while sending the coins we input 2 fields : Destination Address & Receivers Keyword.
If these 2 match with the receivers address and keyword, the transaction takes place.
So even if the address is changed by any such malware, the transaction won’t take place because the keyword and address doesn’t match (like login id & password pair). And since these keywords can be small, therefore if even this phrase is changed by the malware it will be easily noticed (or we can even type it since it will be small).