Thanks to the many good ideas from folks here, I finally got around to building my own mobile MFT cart. It lives in a very tight space and so I needed to be able to store it compactly, yet have sufficient length for cutting long stock. By nesting a second MFT type top and an extension under the folded MFT3, I was able to accomplish that. Here are a few pics of the set up.
Close up of stowed extension and nested aux top.
Simple $12 boom arm on stored MFT3 taken from right rear corner.
MFT3 being slid to side and one set of legs dropped.
Side by side.
Nested top lifted into position and right side extension installed.
This set up works fine for my needs however the nested top when lifted into position isn't up to the rigors of hand planing. It does work great as an extension, assembly table and material support. To keep the intermediate MFT top from sliding around on the cart when stored, it is simply registered to the MFT cart with a few 20mm pegs. In all I have less than $160 into the cart