Detailed walkthrough here!
So
I have seen my fair share of "play as the bad guy" hacks, but never
really played any of them yet. I think this is an alright start though,
since you only play with the original 151 Pokemon, through a heavily
modified Kanto rife with some pop culture references, and starting in a
different location going in a less logical progression. These are nice,
overall. Yep, you deal with Team Rocket jobs, stealing from museums and caves, but also even committing worser crimes with your brother (who is the rival). And of course, a good Team Rocket is you in the end, since you see just how far things could get and run away. Meanwhile, your brother is brainwashed constantly, Giovanni makes a huge mistake calling Mewtwo a clone, and Mew, the actual mascot of this game, just joins your party and is required for one segment. My party by the way did use Mew for that one section, but it ended up being varied as best as I could: Machamp, Golem, Alakazam, Raichu, Pidgeot, and Vaporeon made up the core members. I should mention the Eeveelution because you can only get one in the game; the maximum you can get is 149 Pokemon as the other two Eevelutions aren't really available since there's no breeding or finding other Eevees.
And besides that, the game did go through quite fast. At least in-game time, since I only spent 13 hours. I played through much of it in February, took a long 2-month break to focus on other things, and then only two days in April I resumed playing this and already finished it. As for cons, there are two major game-breaking bugs that the creator acknowledges, and I put them in the walkthrough. The first one in the captain's room of the boat is significantly more egregious, but either way, you should definitely have lots of testing to ensure these things don't sneak through. Speaking of "testers", why are the Kanto gym leaders called this? They actually don't give badges (you just somehow get them randomly as the game progresses), but what bothers me is that they seem like optional trainers (you gotta talk with them to battle, they at least give a good reward like usual) yet these optional trainers are required for the finale, so you just gotta find them (these "Force" ladies just give vague hints as to where they are), and then they appear to cheer you on as you battle...the Quad Core. And while I always expect challenge in hacks, this finale was too easy, the first three trainers even have unevolved mons and their movesets are just not good. The rematch doesn't do a whole lot to improve other than levels and having Big Fudge battle you at the end either.
But if you put this aside, if you really are contemplating playing a "bad guy" hack (one where you turn good anyways), this could be a first one that works for you.