You're making it all too complicated as I found when I had to run two accounts with different accounting periods side by side. Just ignore the accounting period (OK some of the messages in the Ledger view will be wrong) unless you want to work on the ledgers in relation to one accounting period when you can use Settings>Configure to set up the relevant accounting period.

In Reports, create a custom report with New; give it a new name - I usually include the accounting period in the name - and then configure it for the relevant accounting period.

The main limitation in KMyMoney is that at the moment you can only use calendar years for Budgets and therefore for Budget reports.

Incidentally KMyMoney does double entry accounting without showing you the gory details as would be obvious if you ran the same account side by side in Gnucash and KMyMoney. You see the gory details in one and not in the other.