One thought though: by the time the player has prints for those different hullmods- survey equipment, converted hangar, ecm, won't they have already found a more specialized craft to fill that role?
It's really depend of the play style:
-commission-oriented, yes definitly, it's easy to get a Condor or Drover, and cash is flowing. Survey equipment can be fitted on every support ship. ECM is harder, it seems combat ship are always starving OP for this kind of mod.
-Exploration oriented: really useful in the beginning. Fleets are smaller, much more danger from pirates/scavengers. So even a low-grade destroyer with a flight of Talon and an Arbalest autocannon can change the battle, instead of a Buffallo or Tarsus. Also, I like to use it for SUrvey Equipment because most of the time my true freighter are already fitted with Solar Shielding and Expanded hold.
-Smuggler/zombie/pirate/pather, great for being undetected, so you have to diminish your overall signature by getting fewer, but more generalist ships. Also, because your alignment is most often "chaotic-evil", you cannot choose the ships you want, just the one that are available and scavenged.
Which in the end pretty much reflect my previous statement: nice support ship for exploration, a desperate measure for desperate times, and useless if you are backed up by a faction.