I flew a number of Edelweiss flights and quite enjoyed them, especially for occasional A340s on European routes.

But to be honest there is not much difference from Swiss as far as inflight product goes. Most of the differences are in website and support and they are actually quite annoying and it gets even more annoying for WK flights booked as Swiss (sometimes neccessary for mileage tickets or tickets originating outside of Switzerland, i.e you can not buy HER-ZRH one way on WK website).

It must be expensive for a relatively small airline like LX to support separate even smaller airline like WK. Is WK branding so strong that cost savings from merging them would not be offset (and probably higher pay scale of LX but I have no idea if this is the case).

It might still be possible maintain a sub-brand but with fully merged IT, reservations and everything else?