Given the questionable programming skills of the devs, my suggestion will likely shot down, as most of the suggestions here are due to the difficulty of adding a feature. Regardless, I want the option to create a limited number of troop presets, where they appear at the top of the selection page with all/offense/defense/spying/cancel when you are choosing units for an action.
For example, I would set an amount of certain units to be selected with a single click for, say, a standard defensive wall or a beefed up wall. I use a wide variety of defense, but not any eldritch or dark things, for PvP, but am forced to simplify what I send in cases of boosting defense after a spy attempt or recalling to defend from an attack with little notice, where seconds can be crucial to arrive in time. Yes, this would mainly benefit defensive efforts, but would also be useful for offense, especially if you could set for all of a specific unit to be selected. And I realize it will be pointed out that how fast you can choose and send is part of the skill that can determine battle outcomes, but I argue that when you do this often and repeatedly, it is boring and monotonous, robbing the game of much of its fun, as well as punishing those who face significant lag.
Further example, as my explanation is not very clear. Clicking on the first hypothetical preset, whether customizable in name or not, would select five hundred griffins, four hundred demons, four hundred golems, and eight hundred nomads, which could then be sent immediately instead of having to go through and select the numbers individually. (that's not the size or full list of units I actually use; SUCH SENSITIVE INFORMATION IS A CLOSELY GUARDED SECRET XD)