Not having flown a 172 for a few decades -
Make the wing from composites - Lighter, & less parasitic drag
Cut back the inboard LE (a la some old cabin Wacos) for visibility
Restore the straight tail (from the 50s/early 60s) - less friction!
Constant speed prop - and integrate w/ throttle (single control knob)
Optional taildragger (like the original 170B)
Making it into a 182 defeats the purpose - consider cost of operation!