I didn't suggest Calder Valley for 170s, but they would be suitable for Leeds to Nottingham. Are they even route-cleared via Bradford Interchange anyway? I know they are cleared via Brighouse as TPE ran them that way, but the current Wigan services on that route are too stop-start for 170s much like the rest of the Calder Valley services including the Blackpools.
Not sure there are many routes besides the Nottinghams that would be ideal for 170s, mind!
The problem with the Nottinghams is platform space at Leeds. The current arrangement is for a 2 car to sit on 17, with the 2 car stopper coming in on top. The platform can only accommodate 4 23m vehicles. I'm not saying there isn't a solution with the current timetable, but as soon as TPE reintroduce more of their services, things become more difficult. Unfortunately Leeds is a massive pinch point just by the nature of where the Midland lines are (in essence, these trains can only use 13/15/16/17), and to use anything other than 16 & 17 creates a junction conflict.
Undoubtedly, the 170s would be great for Nottingham - I agree entirely, but at present, Leeds capacity is the sticking point.
And yes - 170s are cleared via Bradford as they were the traction of choice for Hull-Halifax pre-covid. Interestingly, they were never cleared over the Calder Valley until a year or two ago. I'm pretty sure TPE never ran them that way due to which depots signed the route/traction etc.