Which is effectively what happens with turning trains around at Reading. Traffic jams happen yes, and people are a bit late, but why should the solution be just throw in the towel, make everything slower all the time or get rid of train services entirely. Also to be clear when a line is closed longer dwell is not going to make a single bit of difference, because you're still sending the same number of trains down. Extended dwells would only allow delays before the dwell to be migitated, however in general delays before Reading do not affect trains too much
Really depends how long you're holding trains, there isn't really space if you want to make a noticable difference. Heading away from London you have platforms 7, 8 and 9. One of these can't be used at points when you're running full service as it is used by CrossCountry, so you cant rely on it 100% of the time. Using 2 platforms in the up direction allows service recovery, and regardless none of these platforms can by accessed by trains travelling from the South West, so would have limited usefulness, with a conflicting move out of the platform across the Up Main.
You then have Platforms 10 and 11. If you wanted you could use these platforms to extend dwells, however if both are filled at the same time it harms service resilience, as a train out of the correct order would be forced to wait behind a train it should be in front of, increasing its delay. So using these two platforms for extending dwells you can extend them until the next train arrives, in general this is about 8 minutes, not much longer than currently, I don't really see a significant benefit to this, a slightly late train might now make its path, but realistically the benefit to anyone is minimal, the passenger gets to their destination a few minutes earlier.
Platform 12 needs to be free for trains on the Down Slow, Platform 13 & 14 are often used simultaneously by the Elizabeth Line, in the peaks, and GWR services stopping outside, Platform 15 is used for GWR Stoppers in the peaks, and depot moves, freight etc out the peak. There is very little space to be timetabling in long dwells.
