I think there should be a type of mine cart thatis faster than powered rails.It would need a some thing like an engine.The engine would be made like this:
The minecart is made by putting the engine on top of a minecart.The mincart would go 10 m/s.
The next idea would I have would be like the could be moved while your in it.There would be two types.They made by putting a normal minecart in the center with powered minecarts or what I have on the top on both sides.They would move a fast as the minecarts used.
If you think their is an issue please say what it is.
you may be right because that is a bit expensive but still powered minecarts are pretty much useless due to the powered rails.It could be made so normal powered minecarts will go faster with blaze powder for a few minutes.