As you probably already know, Pain Killer part of Medi-Kit is totally useless and nobody use it. It is much easier and beneficial to just kill an alien to restore morale lost from a wound. And, what is even worse, there is no indicators of "soldier's pain" in the interface, that is you can see that soldier's morale is below 100, but you can't tell if it can be improved with Medi-Kit.
The most simple solution to revitalize Pain Killer's mechanics is to make pain more "persistent", so that pain prevents achieving maximal morale. If, for example, a soldier has 20 pain, that it's morale cannot be increased above 80 no matter how many aliens are killed. This will make pain more "visible" in the interface and it will be somewhat important to use Pain Killer to remove that pain and increase morale to 100.
I know, if implemented this will be a downside for a player with no benefits, but realism aspect of a game will improve.
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Another somewhat related issue is penalties from fatal wounds on body parts.
https://www.ufopaedia.org/index.php/Fatal_WoundsAccording to this article's text in normal font, a soldier will receive penalties for being wounded depending on injuries on different body parts.
According to this article's text in
italic font and my personal observation, this is a lie and penalties received are not related to body parts.
So let's convert this lie into truth and revive another dead mechanics: body parts.
What do you think about all of this?