I think this is a great feature, not necessarily for someone like me who tries to complete every fusion, especially fragment ones.
But long term f2p's should be delighted. Many say they find fusions too time consuming, too resource-heavy etc... and end up with partial champions. I bet some have 20 or even 30 uncompleted champions. Well, now they'll have a chance to get a free +4. Great deal if you ask me.
And going forward, we actually have an excuse to at least participate in some of the events should we decide to not do a fusion. Before, there was no point at all. I do agree with a post above tat says the 5 extras per fusions are too costly. But between getting 10 (2x arena) and 30 or 40, the required effort isnt that big.