The QoL improvements DE brought to AoE2 (like the grid hotkey layout for building/production or the updated Shift-queue command) contributed a lot in growing AoE2’s more dedicated playerbase, I would like to suggest further, similar improvements, mostly found in other modern RTS games.
-Hotkey + Left Click: Select all visible units of the same type - Common feature in RTS games, typically assigned to Ctrl + Left Click, but being able to change the key is even better. It has the same function as double clicking on a unit but slightly faster and much more reliable, especially on moving units. AoE2 would greatly benefit from this feature as the game is filled with small units that can feel clunky to double click while they are moving, especially during a battle.
-New Hotkey: Select all units of the same type on the whole map - Helps players organize and gather their armies more easily, helps putting them in control groups more easily.
-Quick Cast - Standard feature found in mobas, would greatly benefit any RTS game as well. If this option is enabled, when pressing a command’s hotkey (eg. attack move), it automatically casts the selected command at the current mouse cursor position. It makes controlling armies feel much faster and more responsive.
-Remove maximum selectable unit cap - Players rarely exceed this number (and almost never do in a competitive game), and when they do it feels more like an occasional inconsistency in controls rather than an integral part of the gameplay (like in SC BW). It always feels dubious when exactly will you exceed this number with a drag selection and which units will be included in it, it just makes for a less consistent/reliable controlling experience.
-Make it possible to add units to multiple control groups - Common feature in RTS games. Gives further control possibilities, like having smaller groups also be in a larger group, as sometimes you want to control them separately, sometimes together.
-Make it possible to remove the ingame numbers indicating a unit’s control group - The least impactful change, still, it should be mentioned that it is fairly useless to see these (hard to clearly see) numbers After you’ve already selected the group, it’s needless visual clutter. I also assume that these numbers might be a reason why units can’t be assigned to multiple control groups.
-Smart Selection - While Left Clicking, the cursor gets a slight extra range where it selects the closest selectable unit. Just another slight help in making controls feel smoother when selecting individual moving units.
-Pressing multiple control group hotkeys simultaneously or rapidly after each other adds each of them to the selection - Works similarly as the original ‘hold shift while pressing control groups to add each of them to the selection’ function, but with this Shift can be used for it’s new function (appending units to the selected control group) withouth losing this old function of selecting multiple control groups at the same time.
-Option to rebind alt/shift/ctrl functions that currently can’t be rebound (eg. Shift’s to select add units to selection) - Goes along with the next requrested feature.
-Option to use keys other than ctrl/alt/shift as modifier hotkeys - Keys like Space/Tab are far more ergonomic to use as modifier keys in an RTS than Ctrl/Shift. It’s extremely overlooked how much easier it is to press eg. Space+5 to create a control group instead of Ctrl+5, this part of the traditional RTS button layout greatly discourages newcomers and even intermediate players from making a bigger use of these features, so it would be good if they could be customized more freely.