Like I said, the average consumer stick is all plastic except for the screws, and a lot of them are plenty durable.
I'm not sure how valid your point is here. You've made a big jump between a PC flight stick and an arcade trigger stick.
How so? PC sticks are typically placed on a desktop or in your lap and are used in a sitting position where you really only use your wrist to control it. It is probably impossible to ever damage it using it in this manner, especially since the base is free to float.
Now take that same flight stick and bolt it to a 300lb. cabinet (i.e., not movable), stand in front of it, and use your shoulder & elbow to control it. HUGE difference. What I'm getting at here is that if a plastic joystick shaft is that strong, why weren't they (or aluminum, for that matter) used on arcade machines? Because they wouldn't last. When I worked in plant production ergonomics, these are exactly the types of things we considered when spec'ing or designing new equipment and tools.
Don't get me wrong, I'm NOT saying that using a standard flight stick with a plastic shaft wouldn't work on a home arcade machine. I'm only saying that a direct design comparison between a PC flight stick and an arcade trigger stick is faulty. I agree with you that aluminum tube is a step up from plastic, but it surely isn't as good as using steel tubing, which is also readily available in many sizes and lengths. Nutdrivers are only a single source, you can also purchase it raw. Try some local fab shops if you can't find it anywhere else.
1UP, you hacked a trigger stick, you are happy with it, and that's great. Examples like this inspire others. That's what this is all about... the sharing of ideas & tips to Build Your Own Arcade Controls!