I read on BP that some people just get an umbrella policy instead of doing an LLC, so that I could go conventional.I should get response on offer today or tomorrow, then will decide if I need to make another offer or go in another direction on a vacation rental property I am looking at.  

Also get an umbrella insurance policy. 

I have done some research on BP and have briefly read about umbrella policies, what do they cover and are the policies property specific?

Increase your insurance coverage (and get an Umbrella) on the Asset.

To answer more your question you could have in your name with a large umbrella policy or some people simply quit claim the property to there llc after getting a loan, though the loan due on sale clause could be called.

Generally speaking, are Licensed Brokers open to having a new/aspiring REA work under their umbrella if the REA's intent was to solely focus on his or her own RE portfolio?

The term "General Contractor" is a VERY generalized term in and of itself, that MANY various kinds of service providers "live" under the umbrella term of. 

I'm currenty going thru same, had to get an additional umbrella policy. 

If you are worried about liability, just get an umbrella liability policy.

This umbrella term can be useful for not only covering mandatory inspections but also other visits to ensure the safety of your property.