And in the end, every kind of player, who likes the game will donate to the community, in the best case with own maps. While i agree that no gameplay aspects should be touched to keep the original feeling of the game, I think difficulty levels enable more different playing styles and a satisfaction for a bigger group of players. A great mod with an outstanding soundtrack and setting on the first look, but in the end they only included a counter-strike like seek and destroy/ctf gametype and like 95% of the players left, because this was too hardcore/too boring for them and the developers didnt´t include more diversity so far and the mod is only rarely played today. To pull an example why an ambitious mod should always think of all groups of gamers while keeping their original concept untouched is Neotokyo. I guess when the standalone will be released, a huge spike of new players will arrive, including thief veterans that didn´t have a copy of Doom 3, but also many people who might just find the setting, the idea of sneaking around and sniping anyone with arrows (highest difficulty often means no kills) or other things interesting in their eyes and giving them a time to adjust to the mechanics might be easier without getting frustrated by higher difficulty settings. I also played all the FMs I tested so far on the highest difficulty, but I think many different difficulty levels are needed nevertheless.

Hidden dangerous 2 mod difficulty