I was wondering why it’s not possible to set a VAT type for each supplier. Most of the time you choose a supplier the VAT will be the same. Now it’s easy to make mistakes.
Or a standard account / suspense already filled in would be so nice 
Most of the times you select a sullpier, they supply the same type of stuff, isn’t it?
What you describe may be true for your suppliers and the things you buy. But it isn’t true for all users. Pre-filled fields for variable information can lead to complacency and mistakes just as easily as selecting a drop down option.
Vat applies to goods, not to customers. You can create many Sale vat types and use them
This will be solved when pricing levels are introduced, you will be able to set up price/tax combination for separate supplier or customer groups on item level.