There seems to be a lot of misconceptions here but I'll start off by saying that, yes, Nero could have very well absorbed Rebellion like has with any other demonic object but he can't as long as Dante is still around. I'll explain that later but first let me clear some stuff up.
the only reason he absorbed yamato is because of his connection to vergil i dnt believe he can absorb rebellion and if he could it might change nothing except his moveset
While it is true that he was able to absorb Yamato because of his connection to Vergil, we're not exactly sure why it happened. Nero's absorption ability generally happens through touch but his absorption of Yamato was seemingly triggered by his emotional state. Even more so, his connection to Vergil is through blood but so is his connection to Dante. If blood is the basis of why Yamato reacted to him, then Rebellion should have had a reaction to him as well just not as strong. I should also note that Yamato didn't react to Nero's existence at all until the point of his close call with death.
Rebellion isn't really as demonic as the other things
Actually, it's pretty dang demonic considering it needed a blood sacrifice from its own master to unleash its full power.
its linked to Dante (which is why Dante can call it back and it comes to him). Even Nero tried I doubt he can absorbed Rebellion due to Rebellion not accepting Nero as his master.
Rebellion doesn't really have a choice of who its master is. It's an embodiment of who Dante is, a physical manifestation of his soul and persona.
You can see this in its design changes in DMC 2 and DMC 3/4 as the blade becomes simpler in design as Dante matures.
Yamato is the same way. Since Vergil is a man who embraced darkness, Yamato is a blade forged in darkness. When Vergil was corrupted, it became large and bulky representing the change in Vergil's soul and body. So it is clear that Yamato is just as intimately tied to Vergil as Rebellion was to Dante.
if your theory was possible then dante would have a different dt when using yamato but he doesnt as it was made for vergil
That's actually not true. In DMC 4, Dante's DT never changed at all, so no weapon at the time could have affected his DT. However, in DMC 3, It could be very well possible that Dante's DT would have changed if he held Yamato but that's just speculating.
Same thing would go for Vergil.
Anyone with enough strength or demonic energy can use Rebellion but there are other uses or bonds that must be achieved to use Rebellion's full power such as Devil Trigger. I doubt Dante can devil trigger with Vergil's Yamato (considering he wielded it in DMC4) or that Vergil can devil trigger with Rebellion (same goes for Nero).
You have to remember that Sparda had both blades first before giving it to Dante and Vergil, so the two weapons, while intimately linked to their respective twin, aren't necessarily meant for just Dante or Vergil. Rather Dante could wield Yamato with as much skill as Vergil and Vergil could wield Rebellion just as well as Dante does with both being able to have DTs for those weapons.
Rebellion without Dante is basically Force Edge without the completed amulet.
That's true but not completely. When Rebellion's power was activated, it remained so regardless of who was wielding it.
in the series we see that the best way you can get a Devil Arm seems to be from it choosing you, because it's just another, baser form of the soul. Alastor choose Dante because he withstood impalement, while Ifrit chose Dante because he withstood its fire, and in DMC3 we see that (sans Beowulf) the demons acknowledge Dante's capabilities and relinquish their souls to him in the form of Devil Arms.
I can imagine Rebellion being no different, and Stylish Nero mentioned a bond which I think is important to what I'm sayin' too - the Devil Arms Dante has acquired during his exploits have been mostly given as some sort of prize specifically to him.
The idea here is that they only work for Dante, because they chose Dante, so the bond can't be broken, and Nero can't absorb Rebellion.
Actually, this is true for some and not true for others. While demons like Cerberus and Nevan chose Dante as their master in their weapon forms, others were forced into being his weapons. In DMC 4's case, all the weapons didn't have minds of their own (seemingly), so they were simply taken and used. In DMC 1, Alastor was trying to enslave Dante and Ifrit was simply trying to burn him alive. Dante just fought back and took control rather than them willingly giving it to him. Beowulf also had no say in his master. When Vergil killed him, his soul just went straight to Vergil.
Now, with all that said, I can conclude by saying that the reason why Nero could absorb Rebellion is because of the simple fact that it is a Devil Arm and that the only reason why it would be an exception is that Dante is still alive. From what I can tell, Nero trying to take Rebellion would be like a person trying to go up to a lady and steal her purse by just grabbing it.