iRule data group

I don't think SNMP is the way to go. In lieu of iControl (probably the best way), you could partially automate the process by first uploading the flat list of IP addresses. Example:

10.70.0.1/32
10.70.0.2/32
10.70.0.3/32
10.70.0.4/32
10.70.0.5/32
10.70.0.6/32
10.70.0.7/32
10.70.0.8/32
10.70.0.9/32

And then processing this file with a simple Bash script:

!/bin/bash

data_group=dgimport_ip_list
import_file=iplist

 import the first line and replace everything in the data group
line=`head -1 $import_file`
tmsh modify ltm data-group internal $data_group records replace-all-with { $line }

 parse the rest of the file and add the data to the data group
sed 1d $import_file |while read line
do
    tmsh modify ltm data-group internal $data_group records add { $line }
done

Make sure the address-based data group has been created first.