It worked with thediarygame, clubstatus, burnsteem for several years

This works because the users hope to get a big vote. Most people do what gets the highest votes. That's why it's not very creative...

So extra big buttons at the top

Good suggestion. It shouldn't be that difficult to fade in if the user still has witness vote slots available.

is it possible to write behind the witness what he stands for or does

Each witness has the possibility to store an URL in his properties. This could be a link to an introduction post or something else. On steemitwallet or steemworld each witness already has a button with a link to this URL.