I accept the first sentence, because this is absolutely your choice. But I don't agree with the other 2. Compared to normal miniatures and their proportions to their base, most Titans in the web have way too small bases. That not only looks wrong big time (or a bit like modelling for advantage), but it also is highly unstable and risky. I wouldn't want to risk my Revenant to fall over and break at various joints...
The base should cover the footprint of the entire model (except the weapons and holofins ofc) and should be in scale with the model. Most importantly though it should make sure the center of the mass is sitting safely inside the base. An inscale-base in my oppinion would a base with a diameter as shown:
However, as I said in the beginning, that is your choise and I don't wanna make rules or such. I just believe you should give it a thought, especially because most of the Revenant and Phantom-bases in the web are just oddly small.