Hi Nico,
Of course it's recommended to have the B1i version aligned with the B1 version (taken from the same B1 installation/upgrade package.
In general B1i and B1 taken from different versions are compatible. But please be aware if you are planning to use standard integration content like the sap.mobile scenario or others you need to test them for your specific B1 - B1i combination, first.
Best regards
Bastian