Well I'm sure someone will come along with supper answer for you, but for now:
I think of the last job as my best template. It has all the changes I've adjusted/add etc. I only do residential so sorta simple for me.
You might want two or three...?
Do a Save-As, then;
Just strip out the building/project specific stuff. Keep ALL the generics.
As far as preferences; Options>Working environment>user profile;
If you have not been there before, top option should say custom, hit the
NEW button and name as you choose.
If you move around pallets or ad new ones or tools, and like the new screen layout, go back in and highlight the name of your profile, then you MUST hit Redefine for it to stick.
And of course Attribute manager is the way to bring things in from file you are not doing a Save-As copy from, as mentioned above.
As far as your Master Layout(s), (if I understood you right), I keep mine in in a separate .pln and use "External Content>Place external Drawing" to new/ file if I need to.
Bier
ps, just read your 6.5-12; you probably know a lot more than me!