"...an easy continuous descending 180 degree turn from a base position onto final."
I think you might find that conducting a continuous banked base turn is a tad more difficult than a rectangular one. I believe a student pilot finds a rectangular circuit easier to tackle initially, especially in a GAAP (or whatever it's referred to now...) environment, allowing the student to look out ahead whilst maintaining wings level, vice maintaining/correcting an angle of bank to suitably intercept an extended runway centreline.
And yes, a constant banked base turn in a high winged aircraft does restrict visibility somewhat.
My thoughts anyway...
Joe Lighty