Is there a reason a consumer would want to buy emunies first to do the purchase with instead of just using his/her visa card?
Yes. eMu is the currency and eMunie the platform is an automated decentralised elastic money supply where your not robbed through inflation.
This means they wouldn't buy the eMu for that specific transaction but would have their entire income earned in (or converted to) eMu making financial transactions as effortless and practical as it is with the local fiat currency.