If you do cut it back very hard, you will get a huge amount of water shoots growing. You're best to cut out only one third of all growth in a year, so it take 3 years to cut it right back safely. This leaves enough leaves to nourish the tree, but would not force so much new growth. Ideally, you should do it evenly over the tree.
If you do cut out some of the burr growth, a wood carver would love it for making something small but beautiful such as egg cups - the patterns in the grain are perfect for carving and turning, and I would think unusual for apple. Leave some of the branch either side then store in dry but airy conditions, for the wood to season.
The rest would be lovely on the fire, as it smells good.
I wouldn't try to move such an old tree.