well, right now they treat bitcoins like real money and they don't allow conversion from USD to EUR/GBP/CHF either (and never will),
you can try to convince them that bitcoins aren't that real and actually more virtual tokens than L$,
not sure if you'd be successful though.

VirWox is not exactly cheap,
75SLL+3.5% is for Market Orders only, which are more expensive than trading at current bids/asks anyway,
for Limit Orders you pay 0.8 - 3.9% (*2) based on your amount of SLL commission paid in the previous 30 days.