A few days ago I did cut down an 8"-roll into 8x10s using what you describe as "Plan A". Dahle rotary cutter, feeding the paper roll from the cutting edge side and using the adjustable stop on the table set to the desired length. I too had the fear of scratching the emulsion with the paper clamp. It turned out that with the cutting head in the rest position you can lift the paper clamp and feed the paper without touching it. I have already used fifty to sixty sheets of that batch, none showing signs of emulsion damage.

I also taped down the adjustable stop to avoid the paper slipping under it.