The bitcoin vis bitcoin bond would not have a pegged exchange rate. You would just handle exchange using a system like bit-parking, the exchange rate is just a market price. I don't know what they will be worth either. The market has to figure it out.
Wouldn't the system of linear equations play a big role in regulating the exchange rate between these two (as well as other factors)? And, do you have a hard design for these and their adjustment over time (they are the most critical component of this idea and it would be good to get those out there so we can do verification).
If you use a simple system in which you just mine for one type of block and the proportions of currencies/bonds in each block are constant, then you only need one difficulty. You can set this difficulty using the current algorithm. No modifications necessary. I could make a hard design which allows multiple mining choices and would need a new algorithm. I don't think benefits associated with a new algorithm are sufficient to justify added complexity.
In that case, you have to make sure to set the proportions and the maturity dates appropriately. It would be interesting to run some simulations and see if this is stable (i.e., reaches equilibrium).