I have actually tried to design a levergun feeding AK ammo from AK mags, or possibly 30-30 from Bren Mags. But that would have to be a new design, not an upgrade of a tube fed levergun. Maybe, some day.
I could actually imagine a 30-30 levergun with a folding stock, as it would be practical for vehicle storage. If you had to be able to fire it folded it would take a little more doing, but I think a side or underfolder would work out ok. Kel Tec is planning to release an underfolding version of their SU-16 that has no p-grip and can fire while folded. Very interesting and innovative. You could not use a separate pistol grip on a levergun because even if you redesigned the lever, it wouldn't have room to move as much as necessary.