LifeMiles now allows you to book mixed cabin awards (which it didn't in the past) so you can mix Business and First Class awards, for example, on the same booking. (travelingformiles.com)
Mixed cabin awards price at the highest cabin of the itinerary, meaning even just 1 of 6 segments in business and the rest in economy will price the whole ticket as business (upgradedpoints.com)
However, it does not show Mixed Cabin awards. (milesbriefs.com)