abatonime, at this time the only possibility for oversized emoticons is StuffPlug (http://www.stuffplug.com/),
that way you can add your own emoticons, and they will stay the same size
So you just convince your friends to install StuffPlug too, and then you can use the smileycentral smileys on them
People without StuffPlug will just see them smaller
And I don't really see a problem in sending SPNG to your friends, you'd have to do the same with a possible smiley plugin :/