My opinion about some kind of "transfer TK17 to new engine" - I think its just a waste of time and energy. Much much better thing is always to go with your own project, a new game in making. Mainly because TK17 aside its Pose Editor, which is mainly used, has no other game mode thats too much worthy of mention. "Storymode" in TK17 is just a plain garbage (sorry to say that, but it is).
However it doesnt much surprise that main game mode is pointless, considering when the original game was made.
For example, for my own project on UE (initially UE4 and then later UE5), Im going for a clear main game mode with drastically different approach. UE is especially good engine for more open world type of games. The positive thing is that I can make things in very modular approach and later connect them ... so, for example, customizer (for which there are even already "templates" to buy from marketplace) one can make firstly ... then later internal Pose Editor and main game mode. The main game mode in my opinion, will have absolutely nothing in connection to TK17, but will be either an isometric Sims-like control of player, or third person view (zoomable in/out, rotatable) camera view. The idea for this is to be set in more open world with modular level loading utilizing level "cells". The idea would be for seamless transitions with loading and unloading of "cells", but it can actually go also for more linear approach with loading the "closed" single cell environments (aka, basically our "rooms" in TK17). Further idea is to have a unique system of sex actions in game, which would be intertwined into an RPG system of stats, equipment, skills, etc...
One thing that any xxx game with true vision must have is its internal pose editor. This is a must, and this is not easy. Because one needs to think about exact system of how poses will work and how will they be loaded. Secondly, one needs to think about proper compatible formats - one must have in mind compatibility with many other usual formats (like FBX) and have clear "skeleton" of the game outlayed in such way that it enables modding.
So, to sum it up ... I think transfering TK17 as it is onto a new engine is a bad idea, for someone else who would plan to do it. Because everything around default TK17 is obsolete and archaic. And one should definitely aim for lots of compatibility with transfer of DAZ assets and bodies for a new game. If one would transfer current default TK17 assets onto a new engine, they would literally transfer more than two decades old assets on a new game engine. In other words, pointless.
Instead, the good bodies to base one game would be G3 / G8 and older V4 of DAZ. With additional compatibility for custom bodies and armature. FBX format is standard here.
But the biggest issue will be what I mentioned above ... having a clear vision of how Pose Editor will work, and main game mode will work. For the beginning, its ideal to focus on only Pose Editor, because its a core foundation. Only few XXX games have internal dedicated Pose Editors.