Interesting. Any experience , or have you read discussions, with getting a well scrubbed? Sounds like a good idea. I was thinking of having air blown down from a big engine-driven compressor to remove accumulated sediment, but it would not address the casing walls.A 4 inch casing does not leave room for a sleeve. You could have the casing scrubbed when the pump is pulled.
The CSV should cut down on debris getting motivated and sucked up since it greatly reduces the high volume surging.
A 3-inch pump could have a sleeve (flow inducer), but if the well is cased and bottom feeding, cooling in a 4 inch casing with no sleeve should be pretty good.
EDIT: maybe you were talking about a liner rather than a flow inducer. Even a 5 inch well is not big enough for a liner, AFAIK.