Short answer is no Canadian wireless carrier will allow you to subsidize a dual-sim phone. Reason being is that the carrier wants to be your only provider, therefore by allowing you to use multiple sim cards, that allows you to use service from multiple providers on the same handset.
That means S7 and S7 Edge with Koodo will be single SIM variant.
I do see the advantage of multi-sim phones. Number one reason is for frequent travellers (use a 2nd SIM from a US carrier). Number two would be if you have a work and personal cellular service, and would like to use both in the same handset. Downside is that this drains the battery a bit faster.
If you need a second line, perhaps use a VOIP app (Fongo/Zoiper/etc.) for the second line? Most VOIP services allow you to port a number in, plus there are call forwarding options, if you need a second line on the same handset.