How can I offset an assets pivot orientation?

I have many instances of 39 types of assets. About a third of all the instances need to be scaled along 1 axis. This axis is not a standard orthogonal axis so I can’t just apply with that scale adjusted. Instead I need to find a way to scale those particular assets by a supplied arbitrary axis. My first thought was to use a transformation matrix to alter the orientation of an assets pivot by specifying the new axis. I asked the question before on Answerhub and the response I received was that it’s not possible in UE4 - an answer that I do not like… It was said that even if I could build the correct transformation matrix that UE4 would essentially “fix” the supplied axis by converting it to an orthogonal setup first. This seems odd to me because I thought the idea behind a transformation matrix was to alter the way vertex data is perceived to quickly change the data without it being overly expensive.

I’m new to programming but I don’t mind if I have to make large sweeping changes to UE4 engine code in order to get this working. I’m also open to alternative suggestions for solving the problem. Does anyone know if UE4 would “fix” the offset axis and if not could someone point me in the right direction for offsetting a pivot of an asset so that I can scale it along that prescribed axis?