This thread is making my head hurt. If the goal is to make it sound like a cello, then it needs cello strings. The average scale length of a cello is about 27". If you change the scale length too much, or use strings that are too thick, it won't sound like a cello any more.
As for the height and size thing, anyone can obviously do what they want, but it really doesn't make that much difference. I've played for 15 years with pianist
Harry Pickens. Harry is 6'10", and is a virtuoso. He plays regular pianos, and he has found a way.
by comparison, Jason Tiemann (drummer in the above photo) and I are both between 6'1" and 6'2".
The OP's hands are large, but nowhere near Harry's. Heck, I'm relatively short by comparison, but ...
This means nothing about my ability (or lack thereof) to play the piano.
Harry can reach from the low C up to the A a 13th above, and play notes in between cleanly. I have a colleague who's about 5'6" who can barely reach an octave. He's also an amazing virtuoso pianist. Hand size doesn't mean much at all if the technique is there.
As for the rest, anyone can do whatever they want with their instrument, but I would argue that it's a choice and not a need. I am reminded of a concert I saw years ago featuring Edgar Meyer (bass) and Mike Marshall (mandolin) Edgar has small hands, Mike has giant hands. It was a brilliant concert, and neither had any trouble playing their axe.
