Full disclosure: I am a new XCOM player. I have played a lot of the 2012 version and XCOM 2, but decided to pickup the originals to try them, and I really love them so far.
As a new player, I have had to do a lot of reading in order to understand mechanics. Many things (like 2 handed weapons) aren't even in the game manual, which is quite infuriating as it means we effectively have to go hunting for information.
I propose some changes designed around accommodating newer players and adding some QoL features for veterans, without interrupting the "feel" of the game or the vanilla difficulty/gameplay.
1. Two-handed accuracy penalty when dual wielding is never documented anywhere or communicated to the player, you just have to sort of know about it. There's also no in-game way to know which weapons are two handed AFAIK without going into the "stats for nerds" menu, which seems more like a debug menu than anything else. I propose that in the inventory screen, when equipping a weapon into a hand slot, if a two handed weapon is equipped in the other hand, the other weapon should change to have a red background and a "-20% Acc" text on top of or underneath it, to signify that by equipping this item we are giving ourselves an accuracy penalty with the two handed weapon.
2. Add a "Loadout is Free until First Move" option. Currently, when clicking OK in the inventory screen, it starts the mission, making it tedious/painful to equip soldiers because equipping/unequipping costs TU and they have to move to the correct area of the skyranger in order for the items to appear available on the ground. It also disables quickly applying inventory templates etc. It's very easy to accidentally click OK or need to go to the menu while midway through equipping troops at mission start. This is tedious. With this option enabled, moving items between slots would cost nothing, and all units in the players faction would have access to the Skyranger supplies and inventory templates until the first movement action is taken, so as long as we don't actually move anyone, it's as if we never left the initial loadout screen.
3. Middle Clicking on a characters name in the UI with the Statstrings mod enabled should pop up a window showing what each of the stats strings actually means. Seeing "/wcr" is meaningless to a new player.
4. When right clicking a weapon slot (to set it as preferred for reaction shots), the "Use [Right/Left] Hand Item" text should change for 3 seconds to say "[Left/Right] set as reaction shot priority weapon" to help explain what this actually does.
5. Multi-Level view should have an option to not show a roof if a visible unit is underneath it. This would make it actually really useful if we have units ex inside a building without covering everything up with a roof.