It is said that knowledge is power, and intel is a form of knowledge. Power usually fades, and so does Intel. It is possible to lose access to information that was previously accessible. In some cases, this information will now be displayed as stale.
This is probably my favorite part of all this so far. If you want something, you have to work for it, same with keeping it. I really feel more mechanics in the game should be like this, where things naturally degrade or lose their worth and you need to actively improve or invest in them.
Just spitballing - less advanced armor/weapons are less effective against advanced ones. Their damage is a benchmark, but they have reduced effectiveness depending on the other fleet (and vice versa). This could lead to FE/AE and crisis' being harder to fight because their tech is advanced and/or unknown.
And food could decay, so if you're running a food deficit, you run the risk of starvation.
For diplomatic power, I'd like to have that hidden, or at least specific values hidden until you get more intel.
Are there any changes to enigmatic engineering?
I'd also keep the capital hidden until at least medium Intel. You can find nearby colonies, and maybe a possible capital if you're lucky, but you need more info before you know for sure.