I'm not sure that it is demoralising for them. It didn't seem to demoralise Courtois, Lukaku or De Bruyne for example, all of them went away and improved massively.... Also I think Chelsea's method of loaning players was very different to the method that we had in place under Redknapp/AVB/Sherwood. It seemed to me that Chelsea would bring in foreign players with the sole intention being to loan then straight out, with them often being loaned for multiple years and to clubs overseas. They were effectively just stockpiling talented youngsters from around the World, irrespective of whether they were light in that position in the first team or even in their existing under 21/academy teams.
Our loaning of players contrasted with that Chelsea's quite a lot, we would typically either use the loan system to send the players who had come through our academy out to get proper first team football. Alternatively we used the system to move on players at the other ends of their careers who perhaps we could no longer get much of a transfer fee for, but where we could bring in a loan fee and get their wages covered for a 6/12 month period.
In our last season under Redknapp we had the following players out on loan:
Caulker, Naughton, Byrne, Mason, Obika, Ranieri, Archer, Kane, Parrett, Falque, Carroll, Oyenuga, Smith, Dawkins, Jansson, Townsend, Button, Bostock
I think every single one of those players other than Falque came through our academy (although a couple of them were signed for the academy at 15 - 17 years old). Now if you look at that list of players many of them have gone on to play proper professional football, with 7 of them playing at PL level. That is an absolutely huge return for a club. I doubt that any of the players above were demoralised by going out on loan. Just as I doubt that a player such as Onomah or (for instance) Winks would be demoralised by such a move.