The entire Prunus genus tolerates wet feet poorly, and I notice other potential problem issues with the basic plan. You may find the thread I linked to below of some value insofar as getting you started in the right direction tending trees in containers for the long term.

Al

Here is a link that might be useful: Trees in Containers

Forgive me, please. The thread I linked you to is no longer active because it topped out at the limit of 150 posts. See below for the continuation. I think the information is more effectively presented in the following link:

Al

Here is a link that might be useful: Trees in Containers II

Fig trees also don't like wet feet. The coconut fiber mix that I use for figs doesn't hold to much water. Also coconut fiber takes a long time to brake down, so the potting mix will last for years. Also do potted cherry trees need root pruning from time to time? Fig trees roots are pruned every 2 to 3 years to give them some fresh soil and to promote new root growth.
Anthony

Honestly, it seems like you're telling me more than you're asking me. I'll leave you to your ideas about the soil, which I don't agree with, but that's neither here nor there.

Did you take time to read either of the threads I linked you to?

All potted trees need root pruning on a regular basis if they are to be allowed the opportunity to grow at or near their potential, within the influence of other factors that can limit growth/vitality.

Al