Hi there,
Can we manage the 2 X new ESXi 6.0 with same vCenter?
Yes
Can we add the 2 X new ESXi 6.0 with multiple vCenter servers?
I'm assuming you are asking if you can connect the ESXi hosts to multiple vCenter servers at the same time, in which case the answer is No.
How can we do a shared nothing vMotion with those VMs on standalone ESXi hosts?
The ESXi hosts would need to be licensed for vMotion for this work. See this: Requirements and Limitations for vMotion Without Shared Storage. This means they need to be running (licensed) with Essentials Plus as a minimum.
Is there a way to restrict access for the new ESXi 6.0 clustered hosts for the team managing those ESXi hosts and VMs?
Yes by using vCenter Permissions.
Hope this helps.