Theoretically is it muttur to pasken like a single man de’amar? for example, if someone knew all the Rambam’s shitos on every topic could that person be a “Rambam-nic” and hold like the Rambam in all situations. I know there is a Gemara that says one could pasken like beis Shammai if they wanted to but is this Gemara lemaisa. I’m not asking if one should or trying to do something like this I just want to know if theoretically it was ok to do that.
I have never heard of such an idea. After the Shulchan Aruch was written and Klal Yisroel has a psak, I don’t think one has the right to just change and do what he likes to even though it is consistent with a particular opinion.