When I had a SC I used prefilter baskets in them and before moving bed filters instead of a shower. The
moving beds still collected a lot of mulm and debris at the bottom that would need flushing out occasionally.
With a shower this would be really hard to do so if you go with the shower I'd put matala mats or some type
of additional mechanical filtering at the top of it that could be easily cleaned and help keep more debris out
of the shower media.
It might have just been a logistic in the drawing but no need to put the UV up that high and have to pump
the water higher than necessary.
Sand and gravel filters are usually pump fed from the bottom. They can be fed over the top but it needs
another pipe that feeds the air manifold to clean.
I've seen others feed skimmers to a larger collection barrel but I've never tried it so can't comment on
how well it'll work. I sure understand the desire to clean the baskets less often.