Disconnects are something we all get now and then, many of us also run more than one account. It's really frustrating when you do get disconnected to have to reform your group, especially if your main toon was the one to get kicked. My suggestion then is really simple...
Currently:
Toon gets disconnected
Player logs back in
Toon gets booted from group
Re-invite toon/reform group
Proposed:
Toon gets disconnected
Player logs back in
Server checks if the toon has been disconnected for <less than arbitrary time (eg; 120 seconds)>
Yes; Restore toon to same position in group
No; Boot toon from group