I don't see the Oilers objecting to save a bit of money. At best he's 5th on the LD depth chart with Broberg and Samorukov (once healthy) not far behind.

Why move him for another (worse) LHD though? I'd rather move him for more forward depth, someone on a 2-way who could be a legitimate recall option (as Lagesson is).

Hamonic is already suspended without pay, why terminate him after that

Because they can't spend his salary on a replacement because he may come back, termination means they can go ahead and make a trade for a good RHD and be able to pay him.
I would do much the same except instead of signing Demers I would try to make a trade first. I like the addition of Grant, but would send Highmore down as he has a 2 way contract and I think Lammiko is going to be a good defensive forward.