You cannot insert multi-key sequenced delays in ISBoxer. You can set it so it sends 1 each keypress for a set amount of time and then starts sending 2 every keypress after that and then resets back to 1 after some set amount of time but it cannot send a second key after a delay in one keypress.

The FTL thing works by having a different keybind for each character and letting ISBoxer decide which one is leader (based on the active window) so it sends the correct keybinds to everyone else to follow that character. It works in Rift with a bit of manual macro creation, otherwise exactly like it does in WoW. I would assume that if you can set a "/follow characterX" type of macro to 5 different keybinds, you can do the same thing in EQ.