If we only use appended/prepended drawing then no, otherwise it depends. We can wrap the draw and poll functions so that we call the original functions in the overridden ones. If someone changes them, we still use the changed functions if the other addon is registered first, so Armory doesn’t break other addons. If it’s the other way around, it’s for the other addon to ensure that nothing is broken (also via wrapping so that there is a call stack of draw or poll functions). But I don’t know of any other addon that does this, I think its a solution that nobody used before, so we should be pretty safe anyways.
Thanks for the links, I didn’t know those channels. The pixel offset mentioned above is probably something that needs to be fixed in the Blender layout code, I tried about every combination of rows/cols/splits/boxes you can imagine^^ The tab bar is just not made for any other layouts/widgets. I wish there would be a variable that lets you offset an element by a few pixels, like Zui can do it.
If you (@ everyone) understood the workarounds I paraphrased above, which one do you prefer? New prototype for the second idea (in theory we can now add multiple Armory tabs without having a crammed interface):
Btw, the search menu is fully functional with this, I have no clue why but it’s great 
We need some proper Armory icon, I took one from an Armorpaint commit but it doesn’t look that good in the UI (maybe it’s just slightly too large compared to the other icons?):
Found another flaw: it’s not possible to add custom properties to panels, only to screens (layouts) or the entire window manager. So when you switch to the Armory tab, every opened properties editor will switch to it.