What would your hops suggestions be ? I was going with a very late sorachi ace addition because of its aroma profile. I was torn between doing a cucumber lager and a cucumber wheat, but still lagering the wheat beer to get a really light clean beer
First thing first, do whatever you want. Seriously! You're making home brew and if you want to try something, have at it. That's one of the best parts about brewing your own beer. As long as you're not entering a competition in the light lager category (which you're not), then enjoy!
Sorachi could be a good addition for sure, try it out. If you're going for a light lager, you'll overpower the beer relatively quickly so no matter what you do, I would use a light hand. Also, what kind of lager are you going for; American, German, Czech?
For your bittering hop, use something neutral like Magnum.
Flavor/Aromoa; in my mind, cucumber would pair well with a herbal hop (any of the noble hops; US or EU, Mosaic might be interesting?). To mix things up, you could also add a small amount of the super citrus hops out there to mix it up a bit (maybe push your Cascade to flameout? Citra, Amarillo). Heck, add in some coriander or fresh cilantro/parsley....
Side note, you don't have to brew a lager for a light/quaffable beer. There are plenty of great base recipes on here for light ales (3 crop cream, Miller Lite clone, etc.) that you can tweak which would fit well with your cucumber idea.
I hope you keep us posted on what you do.