The max energy you could donate to the base is 2000...can this be increased or something? :/

Dan has limited it to 2000 energy for a reason.
I dont know what that reason is, but im sure he has a reason.

So people with 10k energy can't donate it and gain 10k experience.

its to stop you from dumping 10K just before ranking up and having an extra 9999 xp head start into your next rank.
as it is now, i still try to plan ahead and dump as much as possible into the base with a neural on to get a 2299 xp jump on the next rank.