hello Audioniek , and thnks for all explanations;
the reason why I asked for this, mainly to be able to test the built images (which carry certain local modifications) before installing them on flash to save the latter from repeated erasures and writes; that said I would like to have a kernel installed capable of mounting an image on an ext2 partition, something that has become impossible with the current u-boot (7.27). which was probably due to the config.
I don't know if you see what I'm trying to come back to?! but I do understand your point about the time and effort you see being spent on something that isn't really necessary.

I will look for a solution by building a u-boot with an appropriate configuration that allows the use of new bootargs that boot an image from usb (as was the case with that of pkteam). I think that will be the best solution.
b Reagards