In order for changes on one task to cause other tasks to be interrupted or assigned, you're going to need to make use of Signals.  For example, after the task is submitted that added or removed approvers, it would do a Signal Throw Event, and then each of the outstanding approver tasks would have a Signal Catch Event attached to them, allowing them to be interrupted.  You could then route back into assigning the approvals out again using the updated list.

I would recommend having some tracking on the table of approvers to keep track of each approval being completed, so that when it routes out to the approvers, it can skip over all of the approvers who are already complete, and only assign to the ones not incomplete.

Additionally, you don't need 9 inclusive gateways to route to the 9 approver tasks.  You appear to be using those gateways the way that Exclusive Gateways work (basically A or B or C or D - only one can be used).  But Inclusive Gateways allow multiple paths to be active at once (basically A and/or B and/or C and/or D) so one gateway could activate 0, 1, 2, 3, etc. of the approver tasks at once.

It might look something like this:

I would definitely recommend creating a test before editing a process you are using actively.

This structure has two different Signals.

There is a task assigned back to Initiator in case they need to make changes while it is in progress.  This has a Save Changes button.  If that is clicked, is sends a signal that interrupts any of the approvals that are in progress, and then it goes back to the beginning to reassign the approval tasks back out (and also the form back to the initiator).

The second signal happens if all of the active approval tasks are completed, this signal interrupts the form that was assigned to the initiator.

This isn't perfect, its just a rough sketch up really, but hopefully this at least gets you pointed in the right direction.

Alternately, I guess you could try to link specific signals to the specific approver tasks, interrupting them if they are removed or starting them if they are added.  But I feel like this is more complicated than necessaru.