Find a way to put bigger gas tanks on the 13 hp engines. They're too small & have to be checked/filled  routinely or they die at wrong times.

I'd want an air compressor & large supply tank mounted on the trailer not affiliated with truck system. That way truck could sit all day & never run. Older trucks may have inherent leak problems that are inconsequential while the engine is running. We power our blowout system with a good size 12V compressor hooked to a 100 lb empty LP tank. Always plenty of air. Trailer has it's own battery, but it's attached to the 3-battery system on the truck with 2 prong receptacle like Shurco uses for tarps etc. So now you have 4 batteries in the system. We've never had the compressor drain the battery system.

On our 1600 gal trailer nurse tank, we mounted an old air compressor tank of maybe 20 gallons? Charge it up to 150# before leaving the farm & it'll blow out the lines multiple times, or at least as many times as necessary for the 1600 gal.

I like hose reels filled with 3" hose & have wireless remotes available for the reel.

I also use a good size 12V demand pump (Hypro?) to pull from a minibulk fresh water tank. Pump is mounted to the tank, downstream is a garden hose & nozzle. Pretty good pressure & flow rate.