Even the size of the RDA matters, as a smaller RDA will give a more concentrated vape. You can mod most RDA to make them perform close/on pair to higher priced (and arguably quality) ones. The RM2 stock is relatively perfect, with the only thing coming to mind that you'd want to mess with being the airhole. Something the RM2 can do that those can't? The way it feeds the juice, which of course you already stated that was a con for you.
Two things on the second point you made. One, I'll take the ability to flood my RDA and have all the excess juice flow back down leaving the coil and wick completely soaked without leaks over dripping a new flavor without corrupting the bottle any day, but that's just my opinion.
Also, if flavor corruption is a concern, why would you want to drip a new flavor in the same wick anyways? You are
vaping Bobas Bounty which is loaded on the bottle, then drip Unicorn's Blood on it. Then go back to Boba's Bounty. Flavor wise, you are not going to get the true flavor at all. Unless you drip very similar flavors/weak juices, there will be corruption of flavor not in the bottle but in the wick. I'd rather carry a little igo-s sealed with me and if I want to drip all it takes is unscrewing the RM2 and putting the IGO-S on. At the end of the day, those of us who did dripping for a while are used to the hassle, so changing an RDA is nothing.
This is just my opinion, but I would never use any flavor on my RDA other than the one that's in the bottle. That on its own will hinder the true clean flavor of the juice when the wick starts soaking different ones. Every time I switch flavors, I take the wick out, wash the RDA and dry burn it. For my ADVs, I don't want anything less than their pure true flavor.