Good news. I actually managed to simulate an Esc-t keypress with System Events. When Esc is pressed, then the Cocoa Text system, waits a while for the next key, at least in TextInput mode.
This worked for transliting two words, which is bound to Esc-t in my key bindings file:
tell application "TextEdit" to activate
tell application id "sevs"
key code 53
keystroke "t"
end tell
Edit
It is an advantage to have a copy of Peter Maurers free Key Codes app.