I get the aesthetic appeal of bricks, but if everyone is soo unhappy with the output, why do people insist on retrofitting....projectors. I've never, in the last 15yrs of owning these cars, have understood why you wouldn't just go with projectors to begin with? It honestly ruins the look of the reflector housings. They were base model for a reason, haha. Don't get me wrong, props to morimoto for making a heckin' super simple drop in that will create a proper projector setup.
To answer your question about the lens though, the diffraction bars built in to the factory glass is meant to assist refocusing and distributing the beam pattern from the oem reflector design. It would disrupt the projector's intended output which is why there is a plain circular section in front of them on the oem projectors. How bad woudl is affect them? idk, never done it but I'd guess you wouldn't get as crisp or clean of a cutoff as it should be.
Take the stock sealed beams for example; the cheaper replacement housings that have plain glass have absolutely terrible light output no matter what bulb you put in it. Higher quality brands like Hella and Raybrigs maintain the diffraction lens for a reason; you won't get that focused hot spot with them and have a fairly even spread with decent cutoff.
*yes its a jeep, I stole the housings from my S13 because I just couldn't take the shitty ones anymore that came on it when bought 2.5yrs ago. I could barely see 50ft
