@JasonMcD - First - I am not accountant, I just stay at the right hotel. But I saw your post and my blood pressure went way up. I get the same from my users and have responded in various forms but mostly like this:
First, I’ll put forth this assertion - if they’ve never used a MFG accounting system, then they really don’t understand the nuances of immediate posting and the problems that occur. In non-technical terms, the idea of posting each and every material transaction to the GL would cause your GL to be huge - real huge. Thus the COS-WIP calculation and posting process exists. Show them PartTran and ask them if they’d like the double-sided entries for every row in Part Tran to show up in the GL. I bet the answer is No Thanks.
But why isn’t there a sub ledger for Inventory? Because MFG is not Distribution/Warehousing alone and is so much more - inventory, labor and a bunch of other transactions. They all have GL Controls, and the COS/WIP function IS the Subledger. Granted, it has to be done on a ‘As Of Date’ basis because of the transaction count and complexity with the GL controls. But it shows what the subledger values are that will hit the GL, and allows a summarization (instead of detail) to be posted to the GL. Isn’t that what a Sub Ledger really is for - to keep massive amounts of detail out of the GL?
Why don’t trans post instantly?
(SoapBox mode = On)
Why would anyone want this? I mean people make mistakes, Edit Lists exist for the exact reason of double checking the work BEFORE it hits the GL. If it was me, I wouldn’t even entertain that question let alone think it warrants a response. The mere idea of a GL that contains erroneous postings and all the associated corrections to go with it it insane. Why even have AP/AR subledgers if that is your thought process… (SoapBox mode = Off)
Hierarchy? It’s only as maddening as your GL is complicated. I guess I look at it like this - MFG, Inventory, Purchasing, etc. - all have their individual transactions and there associated datasets. the money side of those have been boiled down to the constituent parts needed for the GL, based on the GL structure, established by the GL Controls for each transaction. This is the minimum structure possible. At that point all that is left is COS/WIP posting, so I’m not sure what they mean with the question.
Lastly - Stock Status and other reports - and combing data between Accounting and MFG sides to get a ‘right now’ report. A lot of Epicor’s reports are generic and/or based on a generic operating model - and that is how ALL ERP systems are delivered. The expectation is that you will adjust the reports to suit the modified model you operate under. As for combining data - the only way to see all of your expenses in one report it to have them entered/created in only one subledger, but if travel expenses are in both AP and Project Mgmt than that cannot happen - so multiple reports it is - or one new custom report.
Epicor can’t foresee how every company will use the system, so it’s delivered in a useful form with the expectation that everything from the GL to the reports will be customized and created for your use. This is the same with all ERP’s (that are customizable), and of all the ones I’ve looked at, Epicor is right at the top of the list for “Bang for the Buck”.
Hope that helps bolster your side of the conversation 
and if there any real accounting people out there, please correct me if I’m wrong.