The mandala vests are very dream inspiring aren't they. Glad I could facilitate that for you @CheerBear
I find them very inspirational.
Colourwise, you could have more than one, you know. 

for different seasons and such. I'm sure you can rationalise it some how if you set your mind to it! 

Yarnwise, it doesn't have to be cotton, you can use whatever you have, or can get to fit your budget. Being wool allergic, I use mostly cotton or cotton blends, or acrylic. Acrylic is great for these as you can block it and then carefully hot iron it to set it in place and then you don't have to be so careful with it.
You know, if you were interested in doing one of those mandala vest things, I think we could find a basic design that we could 'do our own thing' with and see what we each ended up with. I make mine much longer and wider in front than most patterns as I like it to be sort of enveloping.
I wanted to show you one I designed and made out of a now discontinued multicoloured yarn that I got cheaper than dirt a few years ago.
Photos removed.
Stash organisation, oh, my, that can be so satisfying, and depending on the size, so. much. work. 
I HAD to do something when I knew I was going to have to move house. I bought 60ltr tubs in a grey colour (so light won't fade the yarns) on special from Kmart, had to go back a few times and ended up with 8 for yarns and 8 for fabrics.
I got those clip seal bags (Hercules Large Storage Bags twin zip) and packed yarns by type and colour, snipping about 10cm length of yarn from each different colour, brand, weight and fibre.
I taped each piece of yarn to an A4 sheet of paper and recorded all information next to it in an easily readable from a distance writing size (sharpies are so good) - How many balls etc. Then put that sheet in a plastic sleeve and taped it to the side of the box that I would be facing outwards.
WIPs got put in a box in their own bags, To Be WIPs also got put into their own box in bags with the patterns and notes for what has been decided etc.
It was a huge undertaking but so worth it now. The boxes are water resistant, fade proof, moth resistant, easy to access, and won't need to be resorted for any other moves.
I did similarly with the fabrics and tools, but without the plastic bags and detailed samples on the outside of hte boxes, just general names like 'stretch fabric', 'broderies', and 'curtains' and similar. It was such an amazing help when it came to moving to have it done in such a way,and it still makes it easy to access for checking what I've got. I stood the fabrics on their ends for easy visibility instead of layering them on top of each ohter.