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I love that idea Marco! I have tried it myself, but the problem for me is that the outer poly sleeve is relatively slippery. When I'm playing 78s I often have a stack of the ones I want to play, and with poly bags, I find it too easy for one to be knocked sideways and slide away, perhaps onto the floor.

Yes, nice idea.
@Marco; my cutting tool is a circular plastic device (kind of an inverted cup) with a central screw with a pin, to center it, and a graduated leg at the bottom, holding a cutting blade at the outer end, so you only punch it at the center, hold everything firmly, and rotate the device until you see the paper circle has been cut away. I'll post a photo later. It costed me somewhat 20 euro, years ago. The blades are changeable. I use one of those autoregenerative green plastic design pads as a support, which resists punching and cutting...
The problem is that herein we had standard 26x36 cm paper envelopes, ideal for 10" records, and also a standard 31x41 cm for 12"s... But these sizes they don't make anymore. You cut the surplus with a cutter, then make the hole, and you have a fresh record sleeve/cover/bag/envelope (haha! ) in seconds!
This is mine, but there are other models... If you google cutting tool for circular holes in paper, you'll get many more!

I've done something similar, and I've even written about it, although my goal was to make sleeves for off-sized records.

https://www.tnt-audio.com/clinica/diy_sleeves_e.html