I found out that there are two script functions to achieve this :
PlayerIncrementWarriorUnitCap {Player, Amount}
PlayerIncrementWorkerUnitCap {Player, Amount}
Those only work for Demons of the Past.
I don't know how to achieve this using a trainer/cheat engine.
However you could achieve something similar with working workers by changing the gamedata with the SpellForce 2 Data Editor and setting each unit population size to 0.
First I'll explain how cutscenes works : Cutscenes have multiple takes, each take being basically a path that the camera and its target will follow. The take is a tak file. To make the path of the take, the camera position and the target position are set with keyframes to progressively move ...
As far as I know, there is no current way for that (I would have already added new models to the game if I knew :P)
The only way would be to contact the one that made LightSong and ask them if it is possible for them to convert Blender models into drs file, as they know how those files are ...