I think this will be similar case to Kenny McLean leaving - everyone's immediate reaction is he'll be easy to replace, but when it comes to it any new signing carries a measure of risk - will they settle in, will they maintain the form from a previous club at a new club etc. Kamara and Power etc are decent SPL players, but so was Tansey. Gleeson has caps for Rep Ireland. Both of them have been hopeless for us, so you just never know.
GMS will not be easy to replace either. Youngsters coming in and making an impression are all very well, but GMS is a top player at this level with international caps, who was one of the main reasons our start to the season wasn't even worse than it actually was.
Replacing Lowe at LB is the big challenge though - he has made a huge difference. I'd take Wallace if he's available.
Also who's going to be captain when Shinnie and McKenna leave? Devlin is obvious choice, but with his injury record there's a chance he'll be on the treatment table more than on the park. The only other player who even vaguely resembles a captain in our team is Ferguson and he's only 19!