Having been there at the beginning of the Elder arrangement in the early 1970's.
The idea of having an MS on a JC would at, least in my congregation, not be allowed under any circumstance. No matter how well "qualified" the MS may have been to be an Elder.
When I left in 2001 they still had an Accounts servant, he would briefly go through the accounts with the PO, who would then sign the form.
There would usually be a full audit at the end of the year. Otherwise most times it was just left to the accounts servant.
It must have changed since then.
I learnt last year that the brother who was accounts servant above, at time I left, and for many years before that. Suddenly upped and left , on discovering a few things about the WT, saying he had wasted his life with the JW's. He was in his 40's never married, keeping himself for "New System" , even though his brothers and sisters had got married. Last I heard he had grown a beard and was off travelling the world.