I'm not too familiar with the /en, /sp duel scam or whatever , but it does seem like a good idea , but i believe it's unnecessary , mainly because you would have willingly entered the duel server expecting a duel , and that's what you'd get. Choice of opponent isn't really necessary , and perhaps that's one of the main factors in what makes dueling fun/exciting.
As for your second suggestion , I fully support it , even though i tend not to item duel persons i don't know.
However it would save the staff guys alot of work if the safe trade like item duel were to be added in, theoretically it should be easy to implement as there is already an existing safe trade feature on the forum aswell as ingame , with the use of /duel .