As you know, the I-Mod Team is working on X3GC2 RotGR the past 2 years, and in this time, the biggest hurdles where the shipmodels. We had to find someone, who can make 1 texture out of 40(!!!), this is called texture baking and we had noone able to do that.
We were kinda overwhelmed by this problem and had a long pause in development. The last 4 month, my team and me was adding so much stuff to the mod that the last 2 years look like peanuts compared to that.
First we just wanted to replace all shipstyles and races. Then we thought there must be some new Techs, then Improvements. Lately we have replaced nearly every material of GalCiv 2.
Everything that was possible to convert from X3, we have converted it. Not in all Cases you have luck in a conversion, not all games have enough material to convert or are compatible (try to make a The "Sims" Mod for GC2 lol). Luckily, X3 - The Reunion has such a huge backstory, that it was easy to produce new content with a little help of our own imagination.
Technologies, Improvements, UPissues, Events and dialogues, out of a detailed backstory.
Over the whole 2 years, this became the most interesting job for my team and me, to create something new on our own, but related to the converted game.
Converting alone, can be boring after time, but to create new parts like technologies or United Planets Issues, out of a story, makes fun!
So this is a huge challenge for us, and still many things wait to be implemented or invented. 
Never forget the power of your own imagination, when you create a conversion, it can makes it even more interesting! 
This Topic is thought to be a look into our work and thoughts, so it might inspire you or give you another perspective.
We want to hear your oppinions!