We have done that before in testing, it was a lot worse and makes things a lot harder to manage.
With gradual acceleration and deceleration, rollercoasters aren't really going to be possible, you'll go right over the end if the speed is anything over 1 due to the way Minecraft works.
with the instant change, it can be done easily. and you can achieve the same gradual speed change with more signs, there’s many more efficient ways you would be better going about it.
Here is a custom version with Implemented acceleration and deceleration instead of an instant speed change:
https://cdn.discordapp.com/attachments/418117731150200862/821757423869886494/MinecartSP-acceleration.jar
I don't recommend using this version though as you'll experience all the problems i mentioned above. but enjoy.