So one thing that's been irritating me lately is how unsatisfying the advancement of animal companions is, because they all take a huuuge step forward at 4th or 7th level - besides the constant advancement as per the druid's companion table that is. Over night, a creature suddenly grows one size category, has maybe almost double its former strength and one or two special abilities on top of that. In general, I feel this to be a lot clunkier than the standard advancement of PCs.
Other than splitting up the things an animal companion would gain into several chunk and distributing those over several levels of advancement, are there any existing ideas or homebrews on this? Google and the forum search didn't really net me anything other than lots of rules questions.
TL;DR: the huge step animal companions take at 4th or 7th level is a bit much, is there anything out there to help smooth the advancement a bit?