Pretty much the same as you OP except for some minor adjustments. I'm not letting go of the Brooklyn picks in a sign and trade (at least in combination with Sully..). I'd trade Young for Butler. Sully, Young, and a Brooklyn pick likely in the lottery is too much in a sign and trade.
I do hope WCS falls down to an area where we can trade up to, though. So your targets are the same as mine (Butler and WCS). Middleton and Leonard will likely not be leaving their teams, but I would target them also if Butler doesn't work out. If none of the restricted wings work out, THAT'S when I would target Love, imo.
I'm a huge believer that all we really need is a wing scorer who can score efficiently (draw fouls and/or hit 3s) and a defensive minded frontcourt player with good athletic ability. All I want are players like Butler and WCS. Love would be nice, but that's just icing on the cake for me at that point. With Butler, you have two scorers (IT and Butler) who can go get their's and get the opposing team in crazy foul trouble.
Love isn't really necessary at that point because it's tough to get more than two scorers working together based on past history. Ray Allen had to take a backseat. Bosh had to take a backseat. Love is currently taking a backseat. There's just not much room for three scorers of that degree in this league. Someone will feel slighted most likely. I have more faith in Stevens to make it work than Blatt/Lebron, though, so there's that..I'd try to see if we can keep Sullinger somehow and ride Sully/Oly as the PFs because you really aren't going to get a ton more from Love in that situation than what Sully/Oly could give you combined. I'm not saying Sully/Oly = Love, but in a situation where IT and Butler will get a ton of touches, it really would bring Love's effectiveness down. I'd rather keep the bench stocked with good energy guys.
IT
Smart/Bradley
Butler/Crowder
Sully/Olynyk
WCS/Zeller
This is what I am hoping for. The frontcourt is a little bit cloudy in my head. I would almost consider getting rid of Zeller and keeping Bass in this situation, but I'm not sure. If one of Sullinger or Olynyk have to go in a trade up for WCS, that's when I would consider trying to get Love or retaining Bass for at least the upcoming season. I feel this is the best case because trading for a guy like Cousins may really deplete our resources. I know we have a ton of picks, but I'd try to maintain as many resources as possible while trying to field the best team possible.
Either way we go, Ainge has a lot of directions he can choose, which is exciting.