The quarterback and the non-imports are the most important just due to the fungible nature of imports in the CFL. Thinking about the expansion picks, the Rider defensive tackle Shologan allows the Red Blacks to start him on defence. The Ticat fullback Delahunt can start in a traditionally Canadian position for four receiver sets and then switch off for a fifth non-import receiver who is probably pretty mediocre. So that's two out of seven non-import starters.
The Red Blacks could go with four non-imports on the offensive line, with an import tackle which are relatively easy to find, although Ottawa could take a page from the Ticats book and start two American tackles and have a decent line from the get go. I'll go with four on the line though. If the Ottawans can find a decent Canadian receiver who can start that's seven total. If they go with the two American imports, they'll have to find another Canadian starter on defense, maybe Stampeder Eric Fraser as the safety.
Finding the decent Canadian receivers looks like it might be the hard part.