I'm planning an Orc isolationist character, and want some input. I've never interacted with the orc strongholds other than to wipe one out with a different character. My plan is to limit my interaction with the towns and cities to all but a bare minimum. A few questions come up...

Is there long term storage available in the orc strongholds?
Are there merchants to buy/sell stuff?
Are all the crafting goodies available in at least one of the strongholds?
How hard is it to mod in a residence to one of the strongholds?

I think 3 of the holds got marchants(blacksmith etc.)

Good to know, but I'm mainly worried about storage and housing.

I currently am playing a Bosmer isolationist. There is long term storage in a broken down shack just to the west of the Western Watchtower. If you fast travel to Western Watchtown, just ride a little further west down that road and right off the road is a broken down shack with no roof and only some walls. There is a working bed for rest and a working (hidden) chest that won't respawn (I have tested it for 60+ in game days)