A couple of thoughts........
You can replace the compressor and the coil on the walk -ins, I believe Tecumseh has a 5 yr warranty on compressors, and Bohn similiar on coils, this leaves you with the "box" which should be in decent shape--maybe a new floor or door, but the box itself rarely needs upgrading or replacing.
It's true all new gas equipment comes with electronic ignition, and this does save gas, compared with the older "mushroom cap" or similiar pilot lights. Thermostatic controls on a griddle are a nice upgrade vs the standard Hi/Low controls on ranges, and extra-thick griddle plates are a dream to work with too.
Tilt skillets are a godsend, keep them at all costs.
Hate fryers with a passion, but if you do upgrade them, get two new ones and a "dummy" --a filter pump. The most dangerous accidents happen when people manually drain and filter the fryers. An automatic pump system (like in Mc D's and fast food places) avoids this.
Lessthanwill, I'd like you as friend too, but I must also defend the griddles. In many places I've worked in that had a 36" or larger griddle, we only kept one or two sets of flames on during low periods--no one says you have to have the entire 72" fired up. Two, if you don't have a tilt skillet and want saute off meat for a stew or braise, you can either swing a pan, or use the flat top. You can save and use about 90% of the caramelized meat juices on the flat top if you are on the ball, either scraping the syrup off before it scorches, or loosing it with hot stock and scraping it off with two spatulas. Done it more than I care to say...
Rational, in my opinon makes the best combi oven. Been using Rational since the early 80's, first in Europe, then in Asia. Once you have stuff steaming in the cavity, you can't use it to bake. I've steamed everything in a combi from creme caramel to whole salmon to beans, and it's great, but I'd rather use the oven as an oven or for re-generation, not as a steamer. Far less shrinkage on a roast in a combi then in a regular Garland-style oven, so in my opinion, the combi is best used for roasting and especially re-generation.