So why would you request to connect a battery storage plant, without having any sort of plans for them?
Because it's a bunch of paperwork you need to get in order to see whether what you have in mind is practical. One of the cheaper parts of the whole process so you do it first.
So for a winter week Germany consumes about 9500GWh of electricity. So you need 56.5GW of power plants to run all the time to produce that.
That's not how the maths works demand changes by hour of the day. Basic load generally fluctuates between 40 and 60GW so we're missing at least 4GW more plus safety buffer. And that's Germany's load, we also export electricity and when the lot of Germany has issues with renewable generation then it figures that Poland isn't likely to be in any better shape. If you catch a large enough geographical area then you'll never have trouble in all places at the same time but to capitalise on that we'd need network connections we don't have, and won't have for some time.
Add to that increased electricity demand as companies are switching from gas to electric. Things like glass smelters, things you can't even shut down: You either have 1600C in there or a very expensive write-off.
Honestly just built hydrogen power plants right now. No need to make them methane gas powered in the meantime.
They're quite literally the same thing. Burner nozzles might be different but that's not the expensive part, and it's not like making them able to burn all kinds of hydrogen/methane mixtures would be rocket science (it's turbine science).
Unless you mean fuel cell plants but those don't run on biofuel and municipal utilities have sewage to ferment (those produce methane). They also don't produce (much) heat which thus couldn't be put towards district heating which TBH we should have a whole lot more of.
Then there's yet another factor, and that's inertia: Gas plants have big heavy spinny things that act as dampeners on frequency fluctuations, buying operators precious time to increase or lower production to match demand without the whole network crashing. Yes you can regulate frequency in other ways, like capacitor banks or flywheels, but if you already have a flywheel why not accelerate it with a turbine?