Being able to peg them to a set value of a fiat currency as a percentage I think would help easily know when to trade between them.
For example, select $10,000USD and see what percentage of that ETH is and what BTC is.
This way trading back and forth between non fiat currencies would be clearer without having to do a paper napkin conversion to a fiat to understand if you will make money on them.
Not as much a big deal if the currencies are going up an down together for the most part like BTC/DASH/Doge/LTC, but helpful when one is bucking the trend.
You may be able to do this and as a beginner I don't know how.