GT3, there, are those at KK and SS who also thought it would not work, but here we are almost a year later, after our busiest summer ever, and it's worked. Even our most sceptical ATCO's are now happily using it. The training threw up many problems with the system, as I expect yours is. What is essential information to have on the FDE's? How do we display/represent conditional clearances? And what is just a 'nice to have', etc. etc. These issues are all part of the development of the system and get addressed and ironed out the more people use the system and feedback potential problems/suggestions to the people developing the software via you OPS dept.
ATCO's, I have found, are amongst the worst for accepting change. But if the system is in place elsewhere, and is succesful elsewhere at units which include some of the busiest in the world, and as a result has been proved, then providing you have a good communication line, which can react to the positive and negative feedback then I hope you will find, depsite your scepticism, that EFPS will work.