add pool member in a disabled state

Yes. You can do it with a Merge File. Not something for people that are not comfortable with Linux Command Line (CLI) and VI, but here is an example:

From F5 Command Line, create a file (in your Home Directory is fine):

vi test.merge.file

Paste in the pool with the changes (Note: You can get the information by searching through the /config/bigip.conf file and grab everything for the pool [See Example Below])

If you do NOT have Administrative Domains and Partitions Configured:

pool whatever.the.pool.name.is {
   lb method member least conn
   monitor all tcp
   members
      10.10.10.10:http
      20.20.20.20:http
         session disable
}

If you have Administrative Domains and Paritions Configured:

shell write partition Partition.Name
pool whatever.the.pool.name.is {
   lb method member least conn
   monitor all tcp
   members
      10.10.10.10:http
      20.20.20.20:http
         session disable
}

Save the file.

Verify the file to insure that it is formatted correctly and that there are no obvious syntax errors:

b verify merge test.merge.file

Reading configuration from test.merge.file

No problems found.

Merge the file.

b merge test.merge.file