That doesn't look bad at all. Would be leery of light coming thru the straight pipe, tho. The more bends you have, the more it traps the light. Painting the inside of the PVC with flat black paint would help, too.

My thoughts stem from my Coral tank. Like in the picture below, (an unfinished project) the plumbing along the top edge of the tank, with the reducer 'T' and two elbows on the ends, turned directly into the lower-back of your cabinet. (the 'T' still facing down, tho)
As if you were to take a ruller, and draw a straight line along the bottom of the top-horizontal pipes, and disregard the rest. (and rotate the thing 90 degrees, so elbows go into the back, for intake) Would need 2 elbows, two short sections of pipe, and a reducer 'T'.

For exhaust, one hole on each side, one fan per hole, pointing out, lol.

But not sure about how you'd block incoming light from those exhausts...possibly a Panda film 'curtain' on the inside or block it before entering, or both? Likely tho, once light comes in, it'll bounce all around that cabinet.

Might just be easier to do it the other way you were mentioning, but, this design may be less of an eyesore, lol.

Boittom line: do whatever works. :thumbsup: