i'm thinking most of the obfuscation would come from the peg-in and peg-out transactions. if surveillance is unable to track and link those 2 transactions, then it could be a viable alternative.
Discussion
maybe I'm wrong, but until there's more activity, won't you be relying on time and coincidence of amounts? personally I don't trust sidechains enough to use it for any period of time. also, isn't it true that switching from Bitcoin to Liquid is a taxable event? and then again for swapping back (unless your plan works)?