It looks like you're trying to minimize MSP costs by minimizing failure rate?
For a garrison ship, that's not going to really work. All military ships cost you 1/4 their BP cost per year in MSP to maintain - either continuously while idling at a maintenance location and keeping the maintenance clock frozen, or in chunks when overhauled. If your ship never actually fights and never deploys long enough to actually suffer a maintenance failure, that will be the only MSP expenditure. And by that metric these ships aren't particularly economical.
Also, you could cut out the turret mounting, it's not doing anything for you. If your ship is slower than your base fire control tracking speed, non-turreted weapons get the base tracking speed rather than the ship's speed. Or so I've read.
EDIT: Sorry, I see you're actually planning to dump these out at a jump point for defensive purposes. For that, huge engineering and crew quarters do make sense. I hope you've got a carrier to haul them back to the barn for upkeep, since moving them by tug would be a huge waste.