I might be slightly confused, i'm quite familiar with that, however i do not really understand the problem. RTA operation is nothing new and has been done for quite some time, especially in those areas of the world with night curfews like for example some parts of europe. ATC doesn't really like the effects RTA flying has as directs will change the enroute speed based on RTA criteria.
The time displays as well as the information given by the FMC is more than sufficient, at least on my simple little 737.
Here a rather bad picture of the setup on that plane without the information available on the CDU which is more than enough as well.