Okay, but you are kind of glossing over the point. A an asset you can get for free is likely going to be more sought after than the same asset you have to pay for. Regardless of the extra context you want to add to it, that is the case. So talking about 9-10 teams being interested in him now as the barometer for how much we could possibly get for him at the deadline is faulty, in my opinion.
Eh, I mean, you're not wrong that getting a guy for "free" is probably a better deal for teams who are pretty sure they're going to contend. But let's keep in mind that that cap space isn't really free for a lot of teams. It's either spoken for, or will be, as they sign their own guys back or guys they need. If, say, Pittsburgh is interested in Kovy today, for whatever contract he's asking for, they'll probably still be interested in 6ish months when we offer him at a steep discount and when they've seen that he can still play in the NHL.
You're also going to open up a market to teams like Vegas, who probably wouldn't have traded us anything for Tatar last June, but happily gave up solid assets a few months later when they realized they were actually contending.
Also the return Kovalchuk would get is highly influenced on how well he plays coming back (which is not guaranteed). And if he does play well enough to earn more than Vanek, then that means he is doing more to win the team games and increase the odds of the team dropping on the draft board (almost assuredly guaranteed).
I think this is the real gamble, moreso than whether there will still be a market for him: is he good enough to retain interest into December/January/February, or is he a dud? On a 1-year deal, I guess I don't really care - either he's good enough that we can get something, or he sucks and he just costs the Illitches some cash.
If we're really worried about our draft position, then you start jettisoning goalies in December or January and you don't worry about whatever gains you made in November.
I don't want to sign either of these dudes, but I think Kovy offers way more in return than Vanek, who barely got anything (relative to the quality of his play). If you want to play asset roulette, the guy you should chase is pretty clear. If you don't want to gamble, we should just let someone else take on both of them and throw Svech/Ras into the fire, and supplement them with whatever 800k/1m-ish veteran is still available in September.