I'm pretty sure if Monero has a way to obscure transactions without anyone know who is sending transactions or how much they are, they can obscure the fees too.
Fees are a mechanism for letting miners prioritize transactions and weed out spam; thus the amounts need to be visible to miners.
Ok, well if there is no way to have a percentage based fee in a privacy focused coin, then I would like the fees to be the same as bitcoins where the user chooses the fee, and if they choose a fee too low then their transaction will take forever.