I'm actually in a different boat, and sorta came to the realization that for TSM to cater to everyone's bloated demands (people actually think that they've been a "top-tier team" that can challenge koreans for a while) they either need to get a sister team or need to be smart with who they're acquiring. If I were to do rebuilding, it would go as follows:
Top: Hauntzer, Quas in as sub- One of the giant complains about hauntzer has been kinda two-fold: he can only really play the "meta picks" and often makes bone-headed mistakes from time to time. Adding someone like quas to be a motivator could alleviate both problems, while also adding in friendly competition should he perform somewhat poorly.
Jg: Meteos- No real need to explain this, sven takes up an import slot and is by far a lee sin one trick. Meteos might have less of an upside, but brings a veteran presence that can elevate any team (see: P1).
Mid: No change.
Adc: DL, Forgiven in as sub/split-duties- For me, if you're going to use an import slot on someone then it should have immediate impact. Not only does forgiven bring a skillset which would make TSM immediately better (best western laning mechanics, deep pool, decent map awareness), but he'd also potentially make DL better. That, and having the two best western adc's of all time on the same team isn't exactly a bad thing
Sup: No change, but adding a challenger support to "groom" under bio couldn't be a terrible idea