I've always felt that tech tree is the weakest point in galciv2, otherwise great game kind of falls flat with highly linear rather boring tech tree so I started to do a compleate rewrite of the tree as mod. After little experimenting it seems that galciv2 can handle techs with multiple requirements correctly but the way automatically generated in-game techtree handles them makes tech tree very hard to read since it simply spawns the tech box n times, one from each requirement but continues from the one generated "highest" in tree. So it would be nice if this could be improved for better tech modding ability.
Also it seems that code used to generate tech tree is fairly simple, it goes through the xml file and draws tech boxes in same order, this too could use some improvements. This makes tech tree planning with multi-requirement techs real pain.
Perhaps easiest(?) would be to allow static placement of tech boxes through x,y coordinate values in tech tree view through tag in techtree.xml and then allow requirement line draw from all requirements. This would have minimal effect on current tech tree (only adding coordinates to techtree.xml) but would allow far grater possibilities with tech related mods but would practically solve both problems I described.
EDIT: It could propably also be possible to maintain old functionality with additional flag xml bool value