The only problem with that is tram train are still subject to trial and it seems subject to delay.
The initial plans for tram train routes are already in place (In South Yorks and other parts of the country). Therefore it is quite unlikely there would be one in the short term.
Plus they will look to put them where there is a proven demand, and quoting Edinburgh as an example is probably not the best considering the amount of angst and debate there has been over that line.