Firstly, don’t think its an AFK miner. That will end up in tears. The Retriever’s problem is that people will assume you are AFK because that’s why you bought one…
So saying, my first barge was a Retriever. Served me well - I lost it for other stupid reasons. I fly Procurers and Skiffs now when I mine (rarely). I never AFK in space.
General advice:
Strip miners in the high slots.
A shield tank in the mid-slots - extenders and resistance modules not boosters.
Possibly put a scanner in the mid-slot if you want to optimize asteroid selection. But not critical.
Low-slots: Damage Control and Mining laser upgrades - ditch the DC for another upgrade is valid…
Rigs: shield rigs to maximize tank.
Mining drones and light combat drones (for the rats).
Don’t waste time waiting for them to come back if you need to run. Save the ship - it’s worth more.
You want to be the hardest kill possible incase you didn’t see them approach you. But as always, don’t fly what you would be devastated to loose - someone will enjoy kicking your sandcastle and watching your tears.