I don't know how extensively you can edit playbooks in an online league since I've never played in one but there are some old school block-to-block screens that help with this. Of course these plays don't work all the time since the spacing and passing is still an issue in 2K15 but it is something else to try.
The '94 Knicks have a few for Ewing that have worked for me in H2H games. The nice thing is that Ewing is moving laterally and coming off a screen instead of just trotting to the block and posting up plus your ball handler is coming off a ball screen at the top of the key while the cross screen in the post is happening (IIRC) so your opponent is going to have trouble sagging off to deny the entry pass to the post since he's occupied with your ball handler coming off a screen.
Basically it differs from punch/quick post plays because there is more movement from both your big and your guard plus your guard is a much bigger threat to score. Most punch/quick posts just have your guard dribbling over to a spot on the perimeter and then looking to make the entry pass. In the cross post play they're coming off a screen with a head of steam so you're more dangerous. Sure, your opponent can still sag off like crazy to deny the entry pass but you'll have a much easier time scoring with your guard as a countermeasure. I'll try to post a video later today.
Side note: There's also a Ewing/Starks floppy play where Ewing posts after Starks comes up to the wing and receives the ball. Again, a play like this helps keep the on-ball perimeter defender occupied and makes it harder for them to sag in.
If your opponent adjusts after having seen these plays a few times and says "forget about the ball screen up top, I'm manually going under the screen and sagging my SG into the post" then you just need to start scoring with your guard or do a manual PnR when your guard has the ball on the wing and is looking to make the entry pass into the post. I've had huge scoring games with Starks when people go all-out trying to deny Ewing the ball in the post. That's simply how basketball works though, especially with modern NBA rules and zones. The D takes something away then you have to adjust.
Your opponent could take a 3rd defender and slide them all the way over to the strong side. I did have one opponent who would manually control his SF (so Mason's defender as Mase sets the cross screen) and he would just stay strong side waiting for Ewing and essentially play a zone. Such is life in the modern NBA. It would be awesome if they had a toggle to turn on old illegal defense rules for classic games, not that it'd help the OP's situation.
The basic action of the cross screen play...
Situation #1
The opposing SG is occupied with the ball screen and stays with Starks on the perimeter. The defense plays straight up and Ewing has room to receive a post entry. This is nice against people who rarely control the on-ball defender. If their gameplan is to let the high ball screen play out then switch to control the SG afterwards to sag in to Ewing they're going to have issues since things will happen too quickly for them to execute that.
Situation #2
Your opponent manually controls the SG and goes under the ball screen and immediately sags in to deny the entry pass. This happens to me fairly often.
Two options here since they have successfully prevented a post touch 1) obviously shoot a wide open jumper 2) manually call a PnR. A plain old drive to the hoop is rare because the paint is so crowded when the D reacts like this, calling the PnR opens it up despite the fact that the opposing SG is so low - it sounds weird given the spacing on the floor but it typically works. People I've played botch this defensive scenario with regularity.
On rare occasion you can drive into the lane for a short pull up/floater if the two 5 men are locked in the "battle for post position" animation and the sagging SG is too far towards the sideline. You can aim for the elbow on your drive and sometimes the centers essentially screen the defending SG. You typically can't get all the way to the hoop because both small forwards are on the weakside block clogging things up. You might have more success here if you have a better SG than John Starks, might be able to draw a lot of fouls as well.
Also, not shown in the diagram in this situation but if your opponent goes overboard with his SG sagging (so they're basically outside the left block while the ball screen up top is happening) you can come off the ball screen and shoot a quick three or try to get into the lane for a floater but again, since this cross screen is happening below there are a ton of bodies in the lane at this time.
Situation #3
If you run the high ball screen and the result is this situation, I would recommend calling a new play. If your opponent leaves his SF strong side then you're in trouble. Too crowded and a reversal typically happens too slow to get anything good out of it. It would be awesome if Oakley set a corner screen for Harper (PG) coming up to the top of the key. Even a double screen with Mase to help open the lane up some more.
On rare occasion I've gotten away with calling an absurd manual PnR here where my opponent manually controlling the SF doesn't know what to do and the PnR essentially clears out everyone near the paint and my SF is open for a bounce pass once my SG comes off the ball screen. I wouldn't recommend trying it very often.