I wouldn't use diluted dev more than once. I have no reason to doubt Ilford's instructions on the method you propose to use and it will, in theory allow more films to be developed but take at look at the increase in development time as you get towards the end of the sequence, as one drawback and weigh up as well the extra economy against the consistency of use once and dump.
I would think that the period over which you intend to develop all the films might be important for any changes in the solution.
Call me a coward, if you like, but I just wouldn't risk negs, some of which might be unique by the pour back and re-use method.
If you do go ahead let us all know the outcome. Fortune favours the brave, they say. On the other hand my glass has always been half empty
Best of luck
pentaxuser