Why are people so scared of change lol
Favor items are a mechanic that a number of people are already lukewarm about. Giving this one-choice-per-match system even more sway in a fight doesn't make much sense right now since, as was said, favor isn't working properly for everyone and the items themselves aren't anywhere close to balanced at the moment.
Why exactly do you think we need this? There are piles of items available throughout a given fight that generally have comparable or better effects than the favor items so how much extra 'depth' do you really see it adding?