Simplest redesign is running longer trains - they still need just 1 driver.
Britain’s trains are sometimes comically small (3 carriages) and overcrowded. French trains are 2-3x longer, Russia/China even more so.
Second is standardisation - all of Uks train companies run different stock and it’s ovsoleye
Weight savings can also translate into cheaper bridges and viaducts, though that’s only true for dedicated track. If you’re sharing with freight they are always going to be far heavier.
Much better is upgrading signalling, automating the train, and running far more service because frequency is king for public transit. Many short trains at high headways vs less frequent long trains has the same total capacity but the short, frequent trains provide far more value. When people don’t have to think about the schedule and can just show up and ride public transit is great.
There are also limits to the value of standardizing rolling stock. You don’t want every train set to be bespoke, but there is also danger in every train being exactly the same. If there is a parts shortage or identified design flaw your whole fleet can be grounded all at once. If you have some diversity you can limp along if one design has to be sidelined.