So we're facing a huge dilemma here. Our goal was to have every game use the same engine, but when we really got down to taking a look at it, we realize that it would take a long long time.
First all of the screens need to be converted to MyGUI, which is a great goal, but a lot of work. That work would add a lot of time to the project and we know for a fact that there are a lot of players that want GB now!
Second is that there have been a ton of changes in the engine, which means that it might not play the same. Syncing the AI will also take time.
The other option is to release it as it's own game, going back on all we've been saying. Bringing the critical updates into the GB engine. The worst thing about that is that the screens only support one language. This can be done over time, but we are trying to figure out the best answer for right now.
64 bit support
Async support
Steam lobby support
That we could deliver a ton faster. The price would be the same, whether as a DLC for our current release or as a new game makes no difference.