I asked for a portable version quite a while ago, and I’m delighted to hear that you have your private version working. The lack of a portable version is actually what makes me not use EmEditor all that much (plus, there are some other reasons, I already said that on another occasion).
But please do not delay a regular portable version for developing a U3 one. IMHO, the world has enough proprietary crap and doesn’t need U3. There’s an interesting thread about it on Slashdot: http://ask.slashdot.org/article.pl?sid=06/08/20/0333226. To me, U3 looks like snake oil.
If you’re doing a U3 version anyway, please do so. But I’d really like to have a plain portable one.