Credit to ayunami2000 for making it work, not recommended for public servers yet.
Download in "gateway/EaglercraftXVelocity/EaglerXVelocity-Latest.jar"
Please check for updates regularly if you decide to use it.
When you enter fullscreen via F11 or video settings you can now use regular ESC again to pause and unpause the game and close your inventory and use CTRL as the sprint key without closing the tab.
This greatly improves user experience when you are a new player and don't understand yet that regular vanilla ESC and CTRL+W messes up the game.