Maybe a bad idea, but I wouldn't be able to resist grafting something onto one of the more vigorous suckers. Why let a huge root system go to waste? The new tree would be in a real hurry to replace the canopy to match the root system below. But I'm kind of a grafting addict...so ignore me and let wiser minds weigh in.

it concerns me more.. that you are thinking of planting in july/august.. [hopefully you are thinking a fall planting] rather than what you might put in a hole... dig hole twice as big as pot .... remove all old roots ... insert plant.. refill with what you dug out... move on with life.. yours and the plant ... inconsequential.. IMHO ... if you do NOT want gummosis.. do NOT plant a Prunus .. and it has nothing to do with the hole.. or the soil ... its a systemic disease .. inside the plant... and it hits all prunus.. period ... it is NOT a fungus ... perhaps if you do some reading at the link.. you can better understand gummosis... and alleviate your concerns ... ken ps: neither the willow.. nor the CM is a Prunus.... Here is a link that might be useful: link

When a city tree crew removes a tree, mot only do they cut the whole tree down to the ground, they also grind the stump and usually grind it quite a ways down. It's a rare tree that can come back from that. Although magnolias are notorious for suckering, especially from a stump, they almost never send up shoots from "leftover" roots. The left-behind roots will eventually rot away. The only thing you need to worry about is a good crop of mushrooms over the next many years. Joe

Vegas, organic gardening is certainly not a crock and luckily, many hundreds of thousands of growers are willing to go the extra mile to produce organic fruits and vegetables. You should know, though, that you will have to study up on the nutritional requirements of citrus in general...and figure out how to provide them,organically, within the confines of a container. You are going to have to provide everything that your plant needs; citrus have some specific micro-nutrient requirements. I see nothing in the Jobe's product that disturbs me too much, though it does not have micro-nutrients, also called miner elements. Fish emulsion could assist in providing some key elements, when used in conjunction with your Jobe's. HOWEVER! It really isn't intended for container culture. There are no directions that I see on the label as to dose and frequency. Another aspect that is troublesome is that I can see how repeated use of this product would muddy up your potting mix....fill the so important pore spaces with fine particles. If you were looking for a product with a high Nitrogen analysis, you'll have to go with something other than your 'organic' products. Lots of container hobbyists resort to the commercial soluble fertilizers, while still using using organic methods for the rest of the plant care. I'm not saying that you should, but just be aware that you will have to keep up with the fert. in order to provide your citrus with what it needs. Another factor in the yellowing 'may' be the potting medium. Again, container culture is entirely different that growing in situ. Garden soil or compost added to a perfect good potting medium can result in a mucky, slow-to-drain mixture. Roots can function in that kind of environment, which is why we have learned to provide a potting mix that remains coarse textured and porous. I may not be the only one that would love to see you re-pot your plant entirely. I'd also like to warn you that moisture meters are notoriously inaccurate. Most of us have learned to rely on the most sophisticated digital equipment we have....our fingers. ;-)