This reminds me of the "parallel" services operated out of Bournemouth & Southampton by BEE. I can't see that there will be sufficient demand from both Stansted & Luton to Guernsey to justify even a daily service from each airport.
What are the planned schedules for these two routes ?
The C.I. are simply not attractive enough these days (especially Guernsey) to imagine that multiple services from 4 London airports will be successful, in my opinion. Time will tell.