As others have already mentioned, opening raw files into PS working on them there and maintaining raw edibility is where smart objects really shine. Now because PS uses ACR to handle raw files, that is why parity needs to be maintained.
You tried linked smart objects? The linked smart object in the TIF is linked to a raw file or DNG, which can be in LR, which you can use for further raw adjustments. The SO updates when you open the TIF again, or if the TIF is open in PS you can make an adjustment to the raw/DNG is LR and tab over to PS and watch the SO update. It's slightly clunky to set up, but I think it would interest you. You then wouldn't need to see ACR.
I think you've got to separate conversion parity from having the same UI. For instance, until LR6, LR had no UI for brushing the grad and radial filters, but it could use brush modifications which had been done in ACR/CC. Going forward, I get no value from Adobe putting resources into giving the ACR dialog features that are in LR. SOs are almost the only time I use it, so I'd be happy if they froze ACR's UI and didn't add before/after and panorama or HDR features. In fact, I wouldn't be at all concerned if they simply abandoned ACR in favour of LR.