I'm in the process of redoing my 18x18 block garage so that it is more functional. Part of that is adding storage along the back wall which has no longer functioning door into the backyard and a windows.

There are plenty of other windows in the garage and when I have them replaced, I'm thinking about having the window and door pulled and the spaces filled in with block and then putting a full cabinet and bench system put in along the entire rear wall.

Anyone ever attempted something like this themselves?

Install dowels into the existing block. 

Install the fill in block and grout the cells. 

If being able to reinstall the door and window is important, you could frame the openings and plaster the outside and drywall the inside. 

What is the exterior finish?  Do you care what the repair looks like when complete?