I don't think adding vocals is necessarily going to help anything... it may attract a few more people who may have been too closed minded at first to listen to purely instrumental techno... but if you think about it.. how many popular genres are largely instrumental?
A LOT of jazz... classical.... etc.. you don't see them worrying about losing a listener base or anything because fact of the matter is its just flat out small to begin with.

I think we should just realize that this type of music is only going to attract certain people, and we should concentrate on getting the people we know that like this stuff to stop making excuses and come out to the parties, instead of trying to make up reasons as to why more people aren't getting interested in it. Did all those people who were into the scene years back just vanish??? Do they not like techno anymore?? I doubt it.... they just got bored of the parties... same old thing over an over..
I think if we can get people out of the woodworks who already like it, and have them then drag their oblivious friends with them..... who knows what will happen... they just might end up liking it. BUT
These experiences have to be presented in a proper format... If you take someone to their first techno night you will need to BLOW their minds...... can't just have some tiny dark pub/club with some lame-o lighting and some shitty speakers.... only the diehards will come out for that ... if even...

This means better promotions, better parties, better vibe... better format all around.

That's what got me into techno after all.... not accessiblity.