I don’t think it is apikorsus or even wrong to have a higher moral standard for everyone. The standards codified by Chazal are the standards for the masses. Obviously these will not be the highest possible standards. An individual has every right to hold himself to a higher standard. Doing so is not saying that Chazal were wrong; it is simply acknowledging that Chazal only required you to go so far and you want to go farther. Going beyond the letter of the law is good unless it negatively impacts another area. Besides for the fact that as mentioned, the Rambam expressly says that killing animals is a lack of rachamim: ????? ??? ????
?????? ?? ??? ????? ??? ?? ??? ???. However, if the person is doing this because he thinks that Chazal were backwards uncivilized hooligans who didn’t care about animals then that might be problematic.