Minecart Improvements.

Something I think that would be really cool is if we could make actual trains in minecraft, so say, what if we made some upgrades?

By right-clicking two minecarts with a chain and repeating that (similar to the new leashing mechanics in the 1.21.8 update), you can make trains up to 15 minecarts long!

Also, can we please upgrade minecart speed? I know that if you turn on minecart experiments you can do speed upgrades yourself, but what about in survival where you dont have cheats on? I don't have a specific speed in mind but I think it should be at least faster than the fastest horse possible as of the latest update. 

And what about upgrading the minecart SIZE? By crafting a minecart next to another minecart, you get a "double" minecart of sorts, which can carry double chests and two different items of choice (ex: furnace AND chest, or etc)

Please forgive me if this is an already discussed topic, as I don't want to be repeating everybody else.