My recommendations are twofold.
1) 23mm is a fantastic piece of glass and although many will throw their hands up in horror, if perspective correction is your requirement, do it in post with LR, or CS. Even if you want the panoramic features of a tilt lens you can replicate it with stitching and perspective correction.
2) Laowa 17mm - so frickin' wide you probably can get the verticals the way you want them. Only drawback is that it needs to be stopped down to f11 and above to get really sharp corners.
I owned the 23mm and the only downside is that the 18mm equivalent fov is actually not quite wide enough for UWA and of course too wide for normal WA (e.g. 24mm fov equivalent).
For me personally, I was going to get the 45-100 and even had the dough lined up but then Fujifilm announced a 24mm equivalent prime, the GF30/3.5, which is just what I want so I'll go for that when it comes out (the wallet won't stretch to both).
Just my two cents.
LouisB