If you like the crabapple you can replace it with an Apple Scab resistant variety (this is the disease yours has). One of my favorites is White Angel Crabapple. It's scab resistant, gets unbelievably loaded with white flowers which are followed by thousands of tiny red apples that hang on the tree all winter for the birds to pick away at.

Here is a link that might be useful: White Angel

Serviceberry tree (not shrub) is about the same size as a crab, white flowers in late April, tasty fruit in June, yellow leaves in the fall, gray bark in winter, few diseases.

I'd recommend A. laevis, but many nice hybrid tree forms are available from nurseries.

Here is a link that might be useful: Serviceberry