The biggest mistake I've made was to add far to many switches. A number of them are marginally useful and only so on the most obscure of my contraptions.
- I have two switches for foldable cooling arrays. Why would I retract only some of them at any point? Either I'm in the atmosphere and they are all retracted or I'm in vacuum and it will not matter if they stick out all over the place.
- I have two battery switches. If I need to connect emergency power it should suffice with a single set of batteries. If I need more emergency power it can be added to that single set of batteries.
- I also have two switches for air intakes. Might come in handy if I want to keep the air resistance as small as possible at low altitudes, but a spaceplane launch is just as doable with only one set of extra air intakes. Actually I could do it almost as easy with a single set of air intakes that I keep open all the time.
- There is support for dual rockets AND aero engine, with dual modes for all of them. I have previosly built ships with electrical propeller engines, a dual mode engine for launch, and an atomic engine for interplanetary travel, but how practical is such a contraption and why on Kerbin should I use dedicated switches for it. I should leave those aberrations for the action group switches instead of adding extra dedicated switches that may never be used.
What I wanted on the other hand was better displays. The three 16x2 displays are a bit too limited. I can display most of the information I need to launch into orbit and land, but it is a bit crude to work with and the limited amount of information still leaves the pilot doing guesswork and flying by the seat of his or her pants. That's not the way to do space travel.
So I made a really crude proof of concept in Python for a resource monitor on an old HP Mini 5101 running Linux so I could keep an eye on fuel and electricity in a better way. There was quite a few glitches in the GUI of kRPC when changing from localhost to my local network, but it worked. The current alarm module just indicate warning levels with no way to see how fast stuff is running out. I know that those things can be had using Telemachus, but I don't want the display to look like a physical display on a screen, I want my screen to actually be the physical display.