I have the same issue, but it's an internal cupboard. My full-height rack has large castors on the bottom so that the whole rack can be pulled forwards,

It does require a large umbilical of cables to move with it, but you still need to do this with rack-runners anyway. If you go the runners route, make sure you can pull the equipment far enough forward, completely out of the rack frame so that you can get to the connections behind. Once you've got equipment stacked above and below and the rack uprights at the side, there's not much room to get a hand in, or to see.

I opted for fixed shelves and movable rack


p.s. Otto - I still owe you a write-up of my rack system, I haven't forgotten about it!