The problem that I would have with a trailer for a loader is that I can't have my 14' trailer full of useful stuff. If you are loading into a leaf box on your truck, you are going to have trouble finding room for blowers, hand tools, etc when the leaf box is full at the end of the day.
And I've looked - it seems like it will be hard to find a road worthy trailer that is 36'' wide total. After wheels and fenders, that axle is less than 2 ft wide. Wanna build one ?
If you build a JRCO type blower buggy, you can run it up on your landscape trailer. Then you have your mower on the job site, and any other things that you want on a Fall cleanup too - walk behind blower, Billy Goat Leaf vac, etc. You can easily disconnect the JRCO blower buggy at the job site, leave it at the truck to do it's thing, and have the mower to bag up stragglers, etc.
This JRCO blower buggy
sold here for $175 or less, very recently.