TL;DR
Add a toggle enable or disable the jetpack on the mech armor.What?
There should be a button near the one for the exoskeleton that lets you turn the jetpack on and off. If the jetpack is off, then the automatic flying over things behavior would be disabled and it would be like normal power armor. When it is on, you get the current behavior.Why?
I like the new mech suit, but like the exoskeleton, there are times when I'd kind of like to be able to disable the jetpack.Having the jetpack enabled all the time is a little less problematic than the exoskeleton. Having many exoskeletons can make it nearly impossible to position yourself with any precision. There is a similar issue with the jetpack in the sense that sometimes, I don't want to be directly on top of a pipe or a building, but it's hard to do that, especially with exoskeletons and the jetpack in combination. And when zoomed out it can be difficult to even tell if I'm on top of a building or not.
Also, it's easier to get a feel for a space, where you can and can't build, things like that, if your movement is obstructed by obstacles.
I like the choice to make flying automatic when the jetpack is on. There is almost nothing about Factorio that is based on detailed, precise fine motor actions in a limited timeframe. And having a manually activated jetpack would change this, and change the experience of Factorio.