TL;DR
Flip using F and G whith in-hand entitiesWhat ?
Blueprints can be flipped using F and G. When having an entity in hand, like inserter, belt, UG pipes, ect. it could be helpful to be able to flip using F and G instead of rotating twice.Should both F and G flip any orientation ? Or should F only west-east orientation and G only north-south orientation ? I don't know. I guess I would only use F for flipping any orientation because it is closer to R.
Why ?
Double-rotating is not painful, but in the long run it start to be a bit, and sometimes you just make one rotate, sometimes 3, and then the R key start to cry because being hit too hard.Is it game-changing ? No.
Will it really be used ? Probably not a lot.
On the other hand :
Does it add a constrain ? No. Currently F and G does have no effect while having an entity in hand. Also people not knowing this feature add will double rotate like they are doing now.
Does it looks hard to implement ? No. But I am not a factorio programmer so I actually don't know and I leave this to you.
Is it one of these details any game dev will ignore ? Yes, but on reason why Factorio is the best game of the world is that the devs do add such QOL details.
Examples
When doing rows of furnaces in early game. How many times did you doubble-rotate your insterter ?When doing many underground-pipes stuff, double rotation is frequently used.
When you put down a belt from finish to start, then rotate, then find out that the rotation went the wrong way, it could be helpful to press F or G and correct in a easier way.
Kind regards,
Grob'