It's not cheating if it's a remedy of in-game errors. The GPs are supposed to help Greece; instead, they will help the ottomans and those that are willing to actually join on greece's side will ignore the war and eventually enforce their own demands using the warscore you gained without their help. Taking on an enemy 20 times your size (that's after you get some serious colonies) is fine, but having to take on both them and a GP is not just hard, it's impossible. Well, it's impossible unless you get yourself a colonial empire. But I don't like doing stuff that way. I won't cheat by forcing the gps to help me, but I will use the console to break their alliances with the OE. Restarting 20 times to be able to face them alone just because you got lucky is the exact same thing. It's the exact same thing as reloading, except it takes more time. I also consider the whole 'using your navy to block the straits' thing to be a major exploit as well, but that's a different issue altogether.
Of course, if you don't feel like restarting/reloading/using the console, you can use cuulture techs to become a sp, colonise for prestife and use your influence. But, what exactly is the point in waiting 30 years before you can use your influence to isolate the ottomans diplomatically (with Russia and Austria also bordering them, that's how long it'll take)? You get a main culture population of one million and a bunch of provinces with 7% starting LIT and non-accepted pops (by then, all greek pops will have been assimilated) that are extremely homogenous culturally and will therefore always revolt? Might as well just get your cores and screw the rest. At the very least, you should get armenians as accepted pops. I mean, come on, there were armenian byzantine emperors and they were a an accepted minority in the empire since the beginning. If you're gonna become byzantium, then it's only right.
The way the decision works atm, you get something that looks like the polish-lithuanian commonwealth, but with polish as the only accepted culture. What exactly is the point in conquering the rest exactly, other than to have pretty borders? Sicily is right next to you, has a good population, a LIT much better than yours and doesn't get sphered so it's always fair game. Basically, you have to either get lucky so that the ottos don't get any alliances or use the console to dissolve their alliance, and once you do that and get all your byzantine cores it's basically game over. There's no incentive to do anything else. You can conquer some random stuff just for the fun of it, because vanilla allows you to use non-accepted cultures for regular soldiers, but in PDM you can't even do that (which is how it should be in vanilla as well).
