I started using Ledger for my small consulting business in Switzerland. Here, the internal accounting structure is quite flexible as long as you can output the balance sheets in the required format. My fiduciary asks for PDFs to verify the (legal) accounting norms anyway.
I'm not sure I understand what you ask about rollup, but so far I haven't found a case I couldn't fit within Ledger. For VAT, I have a flat VAT rate that only applies to my turnover so it was simple to automate (reduce turnover by x% and put that amount into Owed VAT).