Reverse spray bar?

You can use the return/output as a spraybar to keep gunk stirred up. The inlet/suction is rarely, if ever, used as a spraybar.

It sound like an UGJ system more than a spray bar

How are you planning to control the tank level and maintain siphon?
It's possible and there are a few threads dealing with it, but you need to think about it.
Personally, I find that surface overflows work just fine for picking up debris as long as there is adequate circulation. The use of fine media is much more important to keeping the water clear IME.

I don't see any problem with it functioning properly. With your standpipe your tank level will stay high if the pump shuts off.
I would say that the idea here is a good start, but if you use a standard spraybar as an intake, those small holes are going to be very susceptible to becoming clogged. If this happens, you lose your drain and will have a flood. Also, looking at your diagram, it would seem that the suction near the bottom of the "spray intake" would be greater than the suction near the top.

Ah, some excellent points, thank you. I'm going to be working on several tanks in the near future and the overflow method seems good but before I go that direction I want to rule out any other ideas that looked better.