Hi Cortex
I agree 100% that you should be able to attache documents to General Journal entries. The feature of being able to attache a document to a transaction is only baked by MYOB.
However, on another note, When I have the situation where some one has paid expenses from their personal account, I create a spend money transaction to Petty Cash and attache the document there. You can then clear the Petty Cash account at the end of each month/quarter/year (which ever is appropriate) by creating a receive money transaction to Petty Cash allocating it to Funds Contributed or Director's loan, which ever is appropriate for the business entity.
Hope that helps,
AlanT