Doesn't rain get in the engine bay from that and rust all your engine components?
Do you have a cool trick to wash the motor without water?
Armor all works wonders under the hood, I get the big gallon size and use it as a degreaser and to shine up the bay. (haven't cleaned under my sonic hood yet

)
I showed some old timers from the so-cal hotrod culture back when I had a truck in a meet and they ate it up. Next time I went to that meet they all had done up their engine bay in armor all. lol.
I was wondering the same thing when I saw the mock-up sketch of that huge vent, which by the way was well done.
Yes some of us do occasionally wash our engine, and yes
mja you have the right idea; but I personally would be concerned about potentially frequent and long durations of rain pouring onto everything under the hood through such a large and open vent.
When I sold my last car, an RSX, several months later the new owner emailed asking me how I kept the engine and bay so clean and looking new. The following is what I wrote to him:
"I have power washed the engine-bay a few times so it can be done, but since new I have frequently rust proofed the engine and electricals which helps prevent sprayed water from seeping into electricals, however a power wash needs to be done carefully. I do short burst onto specific areas while avoiding certain spots like the fuse box, battery, and alternator. Those things of course get splashed but don’t receive the direct force of the spray.
After the wash, I immediately run the engine to dry everything. After dry, I touch up all visible electrical connection, tranny shift linkage, all bolts, and the battery posts with ‘Rust Check’ rustproofing spray can.
Many areas will still look dull so the best thing you can do to give it that new look, which also helps preserve plastic and rubber parts, is to spray tire-dressing on the engine, all rubber hoses and plastic parts; again I would avoid the battery and alternator, but ok on the fuse box and wiring.
Then wipe off the wetness of the tire dressing with shop towels and don’t worry about places you can’t reach. Afterwards everything will look much closer to that new appearance, especially all the hoses, wiring, and black plastic parts. Don’t worry about the Rust Check or tire-dressing getting on any painted parts."