I am going to start with 0% in the first chain for simplicity, then experiment with alternatives by implementing the interest rate later. Less things to go wrong in the initial release.
It should be [conceptually] easy to establish a loanable funds market. Consider that the price of an asset can be modeled as a function of the expected future benefit (F), the time that one has to wait for that benefit (t), and the prevailing interest rate (i), such that:
P = F / (1+i)^t
Note that F and t are fixed in the agreement; e.g., "Party A agrees to pay bearer $F t units of time from now.
BitShares determine P through the market process, leaving only i to be determined as the lone unknown. Basically, set up a market for BitLoans, and i pops out automatically.
In the case of BitAssets they still require fees to be paid in BTS when they are transferred. When trading on the market some of the bitassets are kept as fees. This destroys the BitAssets and thus serves as a kind of dividend on bitassets.
This is an elegant solution that gets around taxation issues in jurisdictions that have income taxes. If you pay a dividend, then that is a taxable event in many places, especially the places where BitShares early adopters live. However, if you burn BitAssets, then no one has receive a direct payment, and the gain takes the form of capital gains.
In places with 0% long-term capital gains, like Germany, this could result in a zero-tax gain for long-term BitAsset holders.