Then, create a model based on the Archer from the Stronghold expansion, albeit with significant modifications, for the fans, let's say for NHF_E.

The issue isn't about "creating" it, but rather about attaching animations to the model in the game engine's format! There's no converter! Therefore, the only way is to painstakingly fit the necessary parts from other suitable models onto the skeleton of the mounted hero from the Stronghold expansion! In principle, the process is understandable, but as they say, you need to take the plunge and do it, but it won't work on the first try, and you'll have to tinker with it for a very long time, and the opposite shore, where the positive result lies, is not visible! In other words, you need to spend a lot of time on something with an uncertain outcome! Unfortunately, I don't have any extra free time for such experiments right now!