Well first of all, I'd like to say that I am following this project with great enthusiasm.
The idea of a (soon) moddable, open source UFO enemy unknown makes me very happeh
Well then, onto my ideas:
1.) An option to have firing modes of weapons cost a fixed amount of TUs.
While this might be somewhat of a problem to implement, balancing would probably be even more difficult.
2.) Different weapon-skills/stats
Your soldiers would have stats for the most basic kinds of weapons, e.g.: assault, heavy, light, explosives
These classes would be attributed to all guns, so then the appropriate skill affects chance-to-hit and maybe
TU cost - positively and negatively.
So for an example say you give your soldier an assault rifle but his skill is lower than 20. His chance-to-hit
would be 75% of the weapons base-accuracy (?) and firing it would cost 20% more TUs.
This would render the firing (and throwing - explosives?) accuracy redundant.
But also would this bring more thought to the equipping process of your soldiers - equipping everyone with a heavy plasma
might not work out as well as it does in Vanilla.
3.) An ability to view your selected soldier's field of view.
Though I'm not certain if this isn't already implemented, a hotkey to view your soldier's field of view would imo be very helpful.
4.) Being able to see a soldier's weight limit and how much is being used up by the current equipment - in inventory window
as well as equipping screen.
Ideas 1, 4 & 3 are realized in JA2 (3 only in 1.13 i think), idea #2 I've seen implemented in UFO Alien Invasion.
Well then, that's it for my 2 cents. I hope my English isn't too bad