to be honest I don't see it.
from the quote you posted I understand that a sidechain could contain different units, some that are pegged 1:1 with BTC and others that have a deterministic, floating exchange rate.
if that is the case, then I don't see the use case for such a scheme. if one wants to use the feature on such a sidechain then he would want to use the unit which carries a 1:1 peg and not the sidecoin. if, for any reason, the amount of available 1:1 units on that sidechain are limited then someone will clone the sidechain and remove the cap.
sidecoins create no incentive for the user, only additional risk.
if they have the choice between two sidechains promoting the same feature, one using a sidecoin and the other a 1:1 2wp, then the 2wp wins every time
Just to carry on this idea, I think this is something most of you fail to realize.
Any innovative feature ported to a 1:1 chain will inevitably succeed over a sidecoin.
Users will congregate to the safest, most risk-adverse chain and the one with a deterministic, floating peg is certainly not it.
Miners will MM only the most popular chain where there is sufficient value therefore there are considerable chances that miners will have no incentive to secure the sidecoins considering it is doubtful they will attract any user in the long run.