Guessing from the Bionic folder structure and the respective readme it looks like all that may be missing is the respective (standard) UI config setting that allows the actual selection of a texture pack like e.g. in AVWW.
If it is indeed that simple (which I hope for since this seems to be a standard feature of your engine), could you (re)enable the setting in the Bionic settings?
I have an idea for a more full fledged graphical modification in mind for Bionic (besides the recolorings I plan to do for the floor tiles once custom floor support is in), which would be much more convenient to use and feasible to create if I would not have to patch and roll back so many files constantly...
Just asking, you know
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