If the problem is mainly verge parking, have you thought about a TRO banning that? Verge/footway parking can be enforced under CPE without an observation period. For a limited stretch of road, it is best signed with yellow S4-3-6 plates, but could be made a zonal restriction using S5-3-7.
Westminster has experimented with 24/7 no loading without vertical signs. Apparently there were no enforcement problems but no-one appealed specifically on the grounds of the absence of plates. A 24/7 no loading could of course trigger a public enquiry if there were unresolved objections. It might be difficult to explain to the inspector that there wasn’t actually a loading problem, but you were just wanting to get rid of the observation period.
Some authorities have resorted to red ‘no stopping’ lines near schools, even though these are supposed to be a whole route treatment.