Well, the OP obviously not into details and didn't think through his suggestion, but since we are at it, new difficulty makes sense.
Here are the arguments for it:
1) hardware advanced since 2015, both consoles and PC. On a PC it's feasible now to have 150 FPS (variable frame rate in-game setting) on detailed maps such as Burning Paris and 70 maxmonsters present on the map;
2) increasing maxmonsters doesn't bugsplat the game due to high MaxObjectsNotConsideredByGC setting;
3) the game isn't new and those players who kept playing have accumulated hundreds if not thousands of hours and learned the game well enough to not feel challenged anymore by HoE, more like frustrated by its "artificial difficulty" mechanics, one of the most ridiculous of which is the "spawnrage".
This builds a solid case for a new difficulty.
But there are counterarguments as well.
1) nobody at TWI plays this game or cares about the game (which isn't the same as caring about the cash flow from the game) enough to feel the need for a new difficulty;
2) TWI has a history of a heavy handed approach, introducing power creep weapons and breaking things (Prohibiting web console admin kicks altogether to address a barely existing abuse case, HRG Kaboomstick, Incision, FAL on Commando, Locust, had to release THREE out-of-band patches in Summer 2022);
3) They are very likely to stick to their bad, almost universally hated by the playerbase, mechanics and contents changes, such as QPs, EDARs, spawnrage mechanic.
Thus, it's very likely that whatever they can come up with will be far from satisfactory.
I would argue that they should team up with community instead. They have a history of making community maps official. Many of these are high quality material and well received by the playerbase, good examples are KF-Spillway, KF-AshwoodAsylum and some others. They could've worked with the community on new weapons as well, instead, they opted to do it themselves and guess what, a good share of their weapons aren't well received by the community and often an object of sorts of ridicule and disappointment.
The CD community came up with rather well tested and well discussed rules for HoE+ which are uniformly well received, don't break the game and are modestly popular. Some of these are:
- steady progression of maxmonsters starting from 25 solo to 70 6 players;
- no EDARs or QPs;
- no spawnrage;
- normalized as compared to vanilla spawn cycle (no random chance to spawn 2FP+6QP spam or 8 stalkers or 10 crawlers squads);
- more big zeds and earlier with emphasis on scrakes, as unfortunately fleshpounds have issues and are thus less enjoyable to fight by the community.
Just one of the many reddit surveys regarding some of these issues:
Overall, teaming up with the community I feel could've advanced the game in this regard, but the chances of it happening are rather low in my opinion. The main obstacles here is TWI is highly unlikely to rollback content, e.g. EDARs and QPs. Stubborn, but it's just how it is. And their general lack of interest. They'd rather do a shark game or a toy story spies game.