start with new racks.
even if you do go with a wood frame on the outside the length of bolt you would need does not make it worth it. The shelves are stable enough with just a few bolts to hold it. I had a similar shelving system temporarily and hated it. was too easy to have a rack full of anything slip and fall, especially when handling hot.
the wood frame on the outside is an ok idea, it would work, but no that well. The door wouldn't be re-usable because it would not fit the frame properly.
Also the paint on the outside of the frame would eventually peel off and release nasty toxins.
I had a single glass door Coke cooler I planned to make into a smoker. I got it gutted and everything before realizing that to do uit right was going to be far more time and money than I was willing to spend. It was far easier and cheaper to find the right vintage fridge and convert that.
Happy to help, you design it and watch the build, but its not going to be cheap or easy.
and if it is cheap and/or easy then its not very well built. IMHO. I believe in doing it right or not doing it at all.