I don't think it really matters when looking at isolated contracts that could have theoretically been signed. One Karlsson or one Stone isn't moving the needle (at least with that roster) enough themselves even if they obviously would have provided better quality bridging and guidance than what is there now. Investing in proper coaching or management like the Isles did might be just what they need, but not only is that not in Melnyk's philosophy of paying for quality, but that is a lot to shift from an already league low player budget.
Right or wrong, what they need is a bold strategy that isn't them pretending they can compete financially with the rest of the league. I think they are destined to fail if they don't do something crazy like this. Business as usual won't work and we saw just how held back some Senators teams in the past were with glaring holes that couldn't be filled due to budget, but could have perfectly aligned had the budget been there.
When you're as crippled financially as the Senators/Melnyk appear to be and incapable of spending anywhere close to the cap ceiling (in real dollars), you can be as shrewd as you want to be, but unless you adopt a new bold strategy like I've proposed a few times, you just aren't going to be able to compete spending closer to the floor than the ceiling. Certainly not long term consistently unless basically everything goes your way.
Their only chance at success is to treat it like a constant conveyor belt of players and be absolutely ruthless with trading everyone in anticipation of contracts required. Use your assets while under control as they approach mid to late 20's and trade them all... every single one... no exceptions. Be a dumping ground for mostly paid dead cap that can be used for assets. Any available cash could be used to bring in FA's on short term contracts to either insulate a playoff team, or be trade bait at the deadline if things go south, thus helping to keep the train moving. They would take their lumps along the way and it wouldn't be consistent year to year, but it would at least guarantee they don't need to do complete tear downs with 4 or 5 throwaway seasons like we're seeing now. We know that it won't be long before this group comes to a head too, and they can't afford to keep this band together either, so it's not a Karlsson/Stone thing, it's an anyone that needs to be paid at or close to peak value thing.
There is no "loading up" or "tearing down", it's just a revolving system with no loyalty and certainly no wasted money on retirement donations for bad play like Anderson these last 3 years.
The big guns got the attention, but they can't throw around mid tier money to underachievers willy nilly like Dorion did at times. It adds up and those are the guys you're more likely to be able to replace adequately. It's not perfect, but there are guaranteed to be holes somewhere, so best to be from a non needle mover like Ceci or Smith, etc., not the guys capable of leading the team.