That's not super hard to do with the Rotax - the filter is within easy reach on the left/front of the engine. I generally use a small cup to catch anything that comes out as the filter is removed and suffer very little drippage.
I am of the opinion that: 1) removal of the lower cowling on an RV-12 is not that difficult a task to perform and 2) a regular thorough inspection of the engine compartment goes a long way to enhancing flight safety. There are a lot of goodies (e.g., wires, tubes, lines, pipes, etc.) trying their darndest to vibrate on the engine. You can also look for any leaking fluids (I have found the 912 to be a remarkably leak-free engine). Regular inspection (maximum of 50 Hobbs hours for me) of the entire engine is a good thing!