I have a issue my main concern is there any way out to restrict the CPU limit on the Business Group level
I haven't seen such option on Business Group or Reservations but you can do a little workaround.
You can create Resource Pool on vCenter with CPU limit and choose that resource pool in reservations for particular Business Group.
They can create as many vms as you set a quota but resource pool will limit them resources.
I know that probably it is not what you are looking for but I cannot hit on any idea.