All forex brokers list their currencies in fractional form (eg USD/JPY, USD/CAD, EUR/USD, EUR/GBP).
I believe since we are trying to look like an exchange, fractional form is the most appropriate way to list bts pairs (eg BTS/BTC, BTS/USD).
There are two different things here. One is the name of the market. The other is the price or quote from that market.
ForEx currency pairs are listed with the first currency being the base and the second being the quote. Which is exactly what we already have. This is the NAME of the market.
Getting a quote on ForEx for USD/JPY would be in JPY (JPY/USD)
Where USD/JPY is the name of the market and the price is in JPY (or JPY/USD)
It is the same in bitshares already.
Getting a quote on USD:BTS would be in BTS (BTS/USD)
I tend to agree with OP that a quote of the price really only needs to identify the quote units. You already know which market your in.
However if you were just looking at a list of various markets, you might identify the quote either by the market name (traditional forex base/quote) or its mathematical terms (quote/base) . Either is ok, i guess, you just need to be clear and consistent.