If LSI cannot support flights to LON or MAN - not even on an seasonal basis -, what makes you think it could support year round flights to AMS? Given the limited connections offered through ABZ, GLA and EDI and the rather small number of passengers using those three routes, connecting traffic from LSI must be very limited indeed.
Even a single daily flight to AMS would provide almost as many seats on an anuual basis as are required to accommodate all passengers currently flying from LSI to GLA, EDI and INV, P2P or connecting...