I would argue that Phaneuf got traded twice, which might be a decent comparable.
The leafs had to take back about $14mil in bad contracts to rid themselves of Phaneuf to us, and we had to take back $13mil(ish) in a terrible Gaborik contract and retain 25% to get rid of him to LA.
There's your baseline.
I'm not sure we'll be able to find as perfect of a storm as the first Phaneuf trade, especially since at that time Phaneuf was still thought to be a #3/4 D-man, which has a lot of value in itself, only that he was overpaid. At this point, Ryan's a skilled forward who is only good for 30 points since he is constantly either hurt or playing hurt. He's a legit albatross, Phaneuf was just overpaid.
The Senators BADLY needed a top 4 Dman, and they had significant short term dead salary that would prevent them from otherwise adding one via trade or free agency (as if we were going to attract a big free agent....), and TOR was right at the start of a rebuild that allowed them to leverage their excess cap space in the short term to dump Phaneuf.
I can't think of any comparable situation that could come up to that and allow us to dump Ryan.
The second Phaneuf trade was more a shuffling of the chairs since we only cleared a negligible amount of money. I'm talking about a trade similar to Bolland (who was insured) being dumped to ARZ for with ARZ getting Crouse for some draft picks. Trades where significant cap/money isn't coming back because I don't think the Senators can stomach that.
I'm sure there would be options out there similar to the 2nd Gaborik trade, where we shuffle the chairs so to speak, but don't really end up clearing much money. That doesn't help the Senators in this context though, because they need to actually clear significant money so they can retain Karl+Duchene+Stone and be able to fill holes else where salary wise, not just move it around like they did in the Phaneuf trade.
If we want to dump Ryan on his own in a productive way that actually clears a significant amount of his salary, I think the two teams who would be targets would be VGK and NYR. I also think it would cost us an A+ prospect. The only two A+ prospects we have are Thomas Chabot, and depending on how high we pick, whoever we'd get with the 2018 pick.