There could be potential idea here, and it doesnt seem complex, if we assume the connection between certain H5 assets to TK17 default UI - so connecting H5 features to something like sliders, or spinboxes, or checkboxes or similar. So, in a way, the way to manipulate with H5 features not only through H5 menu, but potentially also through TK17 UI.
The idea would be simple as switching the _pass input on the flow. For example, a user in game could potentially switch normal maps dynamically. H5 works like that, that it either uses manual ALT+R refresh, but could also use auto-refresh (which is part of extended H5). This way, the logic says, that we could have auto-refresh active, and dynamically switch between normal and specular maps (or possibly even displacement maps).
The only thing that game would need to do is manually replace name of normal map and PBR maps in stage2 and 3 in _pass file. Lets say that default game UI is capable to read the names of our H5 files... then everytime its selected, lets say in spinbox, the game does the operation of replacing the _pass value with the one we selected. And then, the auto refresh of textures updates our visual look of model.
This puts even more potential complexity. Something like JCMs (Joint Corrective Morphs) are heavily underutilized in game (something I do work on new body which is made for long time now). Now, some folks will be familiar with something called "tension" or "stress" maps in Blender. These are like maps that give lifelike impression on model, for example wrinkles on face. As the model is morphed through shapekeys or its armature manipulated, the tension maps activate to certain degrees and strength, making the wrinkles stronger in intensity, or lower in intensity. This is just one example, but other things can be affected, too, like color or similar.
However, our usage in TK17, hypothetically, could go in certain way of connecting the normal map to JCM or even morph. Assuming the auto refresh of H5 files works as intended, the normal map relief / imperfections and specular map glossiness / metallicity and glow could be all very dynamic like. Example could be, we rotate certain parts of body and see clear "tension" on certain areas of it, where specular map would increase glossiness. Or wrinkles that could change in intensity. The questions here would be how to connect H5-TK17 UI - this could potentially work for fixed values in norm and spec maps... we would just choose the already predefined map. But in any dynamic way, both normal maps and specular maps should have a way to gradate their value further, and this would be ideal for slider setting. The real question here is, how to gradate this ...
Now imagine, if one could gradate with three sliders that represent RGB channels H5 files themselves ... normal map would use above logic and in 0 to 1 ranges represent all channels, and it could hypothetically change the XYZ values of dynamically. Or changing RGB values of specular map, seeing the results in real time. Now this assumes there should be a certain temporary file for either maps that could be "hard-saved" everytime its adjusted. Expanded, this would mean capability to link such dynamic changes to above mentioned JCMs, so when part of the body moves or morphs, it also dynamically changes the values of both normal and specular maps.
If potentially possible in such way, it could create very high realism. Visible wrinkles on face expressions or extremities moving, tension on skin (glossiness) on certain moves, or similar features even on clothing.