Add me to the 'impressed' list with regard to Sadie's degrees.
My initial major in college was Psychology before switching to Theatre & Public Address. Both the Psych Dept. & I were much happier with the change. But lots of more non-psych courses (those with great instructors) helped me understand that there was an underlying psychology--even philosophy with any subject.
Jan. LOL on the 'kitchen sink' comment. The very things you are talking about are what I had to do when I was combining lots of different materials--including but not limited to inks, paints, adhesevives & more. These days when I do a 'kitchen sink' a lot of it is based on what I learned about compatibility of materials back when. But there is almost always a chance that it will have an 'uncertainty factor'. That is wha keeps me doing what I do--just like many of us AIs.
I do like having times when I can trust the outcome of any bunch of stuff I'm using, but I wouldn't be happy if I only depended on that aspect of creativity. And I know that's not what you are suggesting, ma'am.
Regardless of whether we are happy crafting as a hobby or using our ability to earn $s, we share a common goal--making stuff with our 'think'.
Having been the recipient of complete lines of several companies products--especially paints--when I was doing pro work, I sometimes had to struggle with my natural inclination to use fewer individual colors that I knew I could make from a limited pallete. That was not my job. But--like several of my peer designers--I could slip in occasional touches of 'make your own' & the company wasn't (very) unhappy.
Which brings me back to the original question of investing in 'lines'. If I were considering offering work for publication, I'd probably go for obtaining a full line of a product I really enjoyed using & was able to experiment with in ways the company might not have considered. And if I weren't interested in doing 'pro'? I might still invest in the whole line for the very same reasons.
That said, however, I truly believe 'collecting' ink colors is always going to be a 'no-go' for me.
My turn to ramble!