I'd definitely agree with you there if I believed that Jones and Stewart were first 11 replacements for Kent but I don't think they actually will be. Gerrard referred to their signings as "low-hanging fruit" recently which was far too candid but does make some sense. Gerrard is signing back-ups for the squad from a pool of players who've previously performed in this league and who also cost nothing. A change from the signing of Grezda for £1m+ who can't even make the 18 man squads any more. Gerrard has definitely had more success with British players, including Scottish based players like Kamara, than he has from the Balkan markets.
I wouldn't put Hastie in that category due to his age. He's more of a signing for the future and one I'm actually very excited about. Signing young standouts from other Scottish teams is something Celtic have been doing for ages and Aberdeen too actually.