Most of my vehicles have had the pistons pushed out of the calipers, the square-cut seal removed, everything cleaned-up, and then reassembled with the original seals. Slider pins/sleeves cleaned-up and lubed, bleeder screw cleaned-up with a touch of anti-seize on the threads.
I have never had a problem doing this. That said...it's certainly NOT recommended in any service manual; and may not work on a caliper that's already leaking. Mine were all fluid-tight, but the pistons were getting "stiff" to move.
Iron calipers are easier than aluminum calipers, and single-piston calipers are significantly easier than multiple-piston calipers. Aluminum calipers generally need the corrosion dug-out of the seal groove(s). Iron calipers tend to be OK in the seal grooves once the sludge is washed out.
It is absolutely easier to pull out the "Visa Wrench" and just buy rebuilt or new calipers. OTOH, I have zero dollars invested in this process aside from the cost of my time, and "shop supplies"--caliper grease, electricity and wear on the wire wheel, some Brakleen, rags, etc.
Example of crusty rubber square-cut seal from my K1500; with some of the scuzz scraped-off with a fingernail. I make a special point of checking the rubber for cracks/deformation. Despite the age and mileage, the rubber square-cut seals haven't been a problem for me. I have had some torn dust-boots which require a "seal kit" to replace.
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Caliper, piston, square-cut seal before cleaning. I've been lucky with caliper pistons--they're not rusted or have flaking chrome. Any defect below the dust seal groove and they're history.
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...And after cleaning. Piston lubed, and shoved past the dust seal and square-cut seal, but not pushed all the way into the bore:
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