I am not sure I would have a parent for the chart of accounts. Instead, how about 2 BOs. One called chartOfAccounts and it would have an attribute called "type" which is a peer relationship to the "accountType table. This gives you a lot of options. Can filter just on one AccountType, can sort and print by account type.
Using Aware, I tend to think of Parent Child where the child can NOT exist without the parent. I.e. Purchase Lines with Purchase headers. or Payroll transactions to employees.
I think of Peer relationship to catagorize or filter or sort. Also, with a chart of accounts, you will want more info in account type. I.e. is balance sheet or income & expense account.
You made it extra tough by trying to make the account a parent of account. There is no good reason to have only 1 BO. You can not post to "Assets", just accounts under assets.
Bruce