Any reason we can't allow some action during opponent's turns?

Sequential turns are unbearable and simultaneous is bad for the metagame.

Personally I can't even stand hybrid, when it turns into sequential turns. I usually end up just using simultaneous despite its problems.

I feel like you should be able to do everything other than purchases (units, buildings, policies, beliefs, etc) and unit movement/actions out of turn. I want to be able to do stuff like looking at menus (or the civilopedia), changing tech and production queues, deals with other civs etc. I see very few significant ways to abuse this and I feel like it would speed things up in addition to giving you something to do during an opponent's turn. Basically, excluding deals with other civs, if it has an immediate effect you can only do it in turn. If it's just changing a queue order that wont take effect for a bit then you should be able to do it.

Anyone see any issue with this?

Workaround: Simultaneous turns with honor system of who is allowed to move troops and when.

Thus both players can build at the same time, and they can take turns with combat movement

Yeah, sequential turns is awful when there's lots of players, since even allies (or people who are at war with the same player) have to take their turns sequentially.

I guess we will have to do simultaneous turns in the future, with an honor system, maybe.

Is it possible now to do that honor system you are talking off?
My friend and i play and use hybrid, we are now the two largest and ready to fight off each others, but we had a for-fun battle before logging the other day.
Battle becomes very random, since you need to be the quickest to move and then there is lag etc... We thought about forcing taking turns, even though we can both move. Just to make it proper and less random.

Yeah anyone can do it, just requires agreement between all parties, if a timer is already enabled then you must allow at least opponent half the timer as well for military...