its actually not such a bad idea. the COPLL algs aren't really any longer than fidrich PLL's. they are both used as finishing moves. the question here is can you get a cube to this pre-COPLL state faster than you can get that same cube to a pre-PLL (post-OLL) state. alot of the fidrich OLL's are in my opinion a little shorter on average than the fidrich PLL's. step 3 in your method basically says permute 6 edges. in some cases, its going to be slow. a painfully slow to flip 6 edges and position them also. lucky for you the chances of that are low. if it happens you could just perm the bottom 2 edges and fidrich the LL.