Okay, I did a little research because I've never done much in the way of keyboard shortcuts. I wasn't clear on what you wanted for things like opening the Documents folder - that is, I didn't know if you wanted to do it from anywhere or after you are already in the Finder. This matters because the first stuff I found for opening the Document window seemed to require you already be in a Finder window or do something like click on an empty area of the desktop which means you are in the Finder.
So, if you are already in Finder, apparently pressing Cmd/Shift/O will bring up the document folder. Or us the "A" key for Application folder.
Continuing with this scenario, the issue would be how complicated would it be, once you get somewhat used to it? Beats me! But it should mean that you can create your own layout that handles it. For example, I put a number of things I want handy in the Function layer. Hold JK to access it and then you should be able to program whatever key you want to be cmd/shift/O. That way your modifier is always JK.
To do it directly, you have several options:
Hot corner command key on the space bar, one of the shift keys, and "O".
Or instead of the hot corner for command, press CV or NM.
I can see how this could get complicated since, depending on what letter key you will be using, you may need different chord keys for different ones.
But with the function layer, you just use the same two letters plus one other.
Which brings us to the other situation - do you mean you want to bring up the Document folder even when another app is active.
Well, I found something on that too. Seems that cmd/option/space will open the finder from anyplace (at least that's what I read and my brief testing confirmed).
Now that is pretty easy. XCV or M,. will give you both command and alt, then just hit the space bar. Followed by whatever other command you need for the specific folder.
But I assume, if not in the Finder already, to get to Documents, you would have to take two steps:
Do the XCV (or other option) to bring up the Finder and then use whatever function layer key you set up for Documents. Or, just for consistency, set up a customized key in that function layer for opening the finder.
I'm not sure I have all this correct. But it might get you started on possibilities.
As for your scripts and stuff, I don't know. Might depend on what you mean by "key combinations". You can have multiple modifier keys (like command) assigned to one key, but you can only have one regular key.
So if your key combinations are things like command, control, option, shift plus one character, maybe it would work if set up as a customized key. But if it a key combination like "QW", then I don't know of any way to customize a key for it. You can have Q or W with the various modifiers, but not both.