Just came with an idea.
In a macro perspective, we don't care much about fees paid to the network during a day is a bit more or a bit less.
Since CER of smart coins are fed by witnesses, how about asking witnesses to change them less frequently? E.G. change once every day. On 00:00-01:00 of every day, each witness publish a new CER; on other hours, don't update it. With this, the smart coins will effectively have fixed exchange rate all day long except that hour.
Now BSIP26 is in place, we don't need to worry about that the fee pools of smart coins will get drain due to slightly "incorrect" CER.
With this approach, IMHO user experience (UX) of an average Joe who wants to pay fee in bitCNY or bitUSD would get greatly improved.
Thoughts?