I've been looking for pictures of the inside of the above mentioned grid based fresnels, but sadly couldn't find any.
Here's the emitter PCB from the 915:
https://www.chauvetparts.com/product.htm?pid=267437&cat=20787If you've never seen the insides of an ETC Source Four LED there's a
How It's Made episode that gives away a few secrets too. To argue against myself, yes, it's definitely more compact than the front face of a 6-in-1 SlimPar Pro, but I still think with a bit of fidgeting it'd be viable to some degree, for the purpose only of creating a fixture with a single lens that mimics the "old school" look of stage lights. That's why I mention the Spectra Par - that's essentially what they're doing, optics aside.
FWIW, I gutted an 8" fresnel and dropped a 1/4 watt par fixture into it. While it does "work" there is a multicolored "litebrite" look to the fresnel lens. It doesn't look nearly as good.
That's interesting. I wonder if a sheet of diffusion upstream of the lens would help to mask that?