So every time I play X-Com, I save every few turns, if one of my best soldiers dies, he doesn't - I will reload the save. So hitting that quick save button basically feels like working on some document, feels like work.
So idea is, make saving a game mechanic, to save you need to spend one move (each character gets 2 moves), so it's not a big difference, but it turns saving into strategic choice.
To further advance this concept, it has to have narrative basis: mental time-travel. You can transfer memories into past, but only to a point when person was ready to receive it. So soldier will need to spend a turn to prepare his mind for receiving data.
And to take this one more step, this technology needs to be researched. Not too late in the game, at least a few missions, which, as a result, basically, will turn into IRONMAN difficulty missions. And by the time when Save/Load tech is developed, player would have experienced loss and would have a squad that survived trough that.
Optionally one save can be loaded only once, and if there are no saves, mission is aborted.