Increase hit chance on consecutive shots

[bishop]

The idea is that consecutive shots on the same target would make it (a little) easier to hit it, since you already have an aim on the target.

Of course this only applies, if neither the attacker nor the target has moved in between. I.e. this is only a temporary bonus within one round / attack sequence.

Not so sure about the numbers, these should either be static or ideally calculated from the raw hit chance.
For static I would go with:
+2% hit chance on the 1. consecutive shot, when former shot did NOT hit.
+1% hit chance on the 2. consecutive shot, when former shot did NOT hit.

+4% hit chance on the 1. consecutive shot, when former shot DID hit.
+3% hit chance on the 2. consecutive shot, when former shot DID hit.

In case of a dynamic calculated bonus, there should be a higher bonus on targets with a low hit chance vs. targets with higher hit chance.
I could also come up with a formula, but first I would like to know if a dynamic hit bonus like this is supported by the game engine and ofc if the devs are interested in this. :-)

[Denthar]

No thanks. Mechanics like this would need to be applied to both your troopers and the aliens to make it fair.

I already get battered enough by the aliens in the early and late games, and it's also rendered a bit moot for your troops if you're fielding Colonels (who seem to quite frequently reach a super human state if they stick to one class of weapon).

[TheOnlySkyfire]

It seems as you mix the simulation with the simulated situation. Our turn based simulation simulates a fight. You might think shooting a frozen target would make aiming of course easier for the second shot. But the alien is not frozen. We just simulate the fight like this.
Rather I would give a penalty to the shot depending on the number of fields you and the alien had moved (simulating the alien and you running) while assuming that a turn simulates the same amount of time.
And if you haven't moved the last turn, then your guy "truly" stood still and THEN I would give you a aiming bonus.

Hmmm... maybe you could accumulate every move on the last turn and every move in the actual turn for penalty, that would be running. The penalty counts to your shot and the shot of the alien => running target and running attacker accumulate. Also instead of moves, one can use the number of different visited fields per round.

Finally, as a additional "reaction fire" option, you might use saved time units to "dodge", which would increase your "account" of "visited fields" artificially, so that the aliens can't hit you easily, thereby making aiming harder for the next round.

That might bring a new tactical decision layers for the mission battle: Hit and run vs. hit or run. Dogde vs. reaction fire.

[TheOnlySkyfire]

An additional idea of measuring your "speed" might be to mark every time unit spend on the last turn and your actual turn if it was done for moving to a new (not in this turn visited) field (crouching might only get the first 2 units marked). Your actual speed (== penalty for shoot and being hit) then is the sum over the marked time units, from the most actual one till the last of you actual maximal time units (your max speed). So you have a "moving window" over your TUs, to sum your actual speed.
For the "reaction fire" alternative of "dodging", every (or every other - if you want to penalize to moving) time unit is artificially marked as being used for moving to a new field. You keep your "speed" during the whole alien turn. Your reaction fire slow down is already incorporated as in this case you have time units left over that aren't marked as moving. 

With that you become slower on TU penalty effects (instantly), because your maximal TUs drop, and therefore your moving window becomes smaller. Those effects should be added on severe wounds, gas etc. (I don't know exactly if this is the case already). Becoming slower by shooting or looking around, opening doors or crouching is more accurately modeled than in my easier approach in the post above. One is becoming faster when moving on also. Your actual weight (making you slower, decreasing your maximal TUs) is also working fine with this. You always have a valid value when you run into reaction fire.
You also get a penalty if you are move first, and shoot late so you have to plan your fire positions a turn before hand if you want maximal hit chance, and while you prepare for shooting, you might not want to break your concentration by reaction fire or dodging around.
You can "dodge" instead of reaction fire to spend the rest of your TUs  for defense. And if you leave your guy just standing around... aiming, he becomes an easier target.

Edit: Spelling (partly)