My main guitar is a custom headless guitar built by Rick Canton, shown here.
I have played several other headless guitars, including original Steinberger GLs. I don’t find that the small body impedes my playing in anyway whatsoever. However, I don’t anchor my hand or forearm firmly against the guitar when playing. I touch the strings lightly with my picking hand for damping.
Here’s me doing some crosspicking on that guitar:
https://m.youtube.com/watch?v=8awvi4kgumU
Here are some outside Gilberts:
https://m.youtube.com/watch?v=V9e5MgksRrE
Finally, here is a detailed thread demonstrating my picking forms, all of which work perfectly well on this guitar:
Maybe a small bodied guitar will interfere with your picking technique, but I think it’s unlikely. In any case, you could develop another mode of picking which will work.