I would stay far, far away from stall tactics. At the very least, we should make this Pokemon fundamentally offensive in nature. This isn't Gen 5 where Rain Stall and Sand Stall were formidable playstyles; weather now has a short number of turns to work with. A playstyle based on lengthening the game is incompatible with short-term, time-restricted tactics. Let's compare the offensive and defensive benefits of the two weathers with which we're playing:
As you can see, both weathers have significantly better offensive effects than defensive ones. Yes, it's possible to make a stall Pokemon that can perform well in different weathers. It is not possible, however, to make a Pokemon that becomes significantly at better at stalling
because of the weather. A 50% Special Defense boost in the Sand for 5-8 turns is nice, but it already restricts us to a pretty mediocre defensive typing and isn't going to make the Pokemon that much better at stalling. An extra Water resistance is nice, but it's not enough to make a Pokemon that much more viable on a stall team. The purpose of this concept is to abuse weather conditions; that cannot be done on a stall Pokemon.
Now, there is a difference between "Stall tactics" and "Defensive tactics". Stall tactics are meant to wear the opponent down with passive damage. Defensive tactics are meant to mitigate the amount of damage a Pokemon takes so it can perform its role on a team for a longer amount of time. Plenty of offensive Pokemon use some defensive tactics; as Deck Knight said, there are offensive 3 Attacks + Recovery sets. Charizard Y appreciates the Water neutrality to help it switch into Bulky Waters and smack them with Solarbeams. But these are not stall tactics, and these are not stall Pokemon.
CAP24 should abuse defensive benefits from the weather. Maybe that's in the form of extra healing from Moonlight or Shore Up. Maybe that's in the form of good enough defensive stats so the Water resistance and Special Defense boost make a difference. But this Pokemon should not be built with stall teams in mind.