Looks like you have done your homework!
Indeed it would be a nice feature to be able to conditionalize the Title attribute. Please take a moment and suggest it via the Wish Form.
What I might suggest is that you create a Related Topics link that points to each of the desired topics. My hope here is that when one or the other topics is removed by conditionalizing, it will leave behind a single link. Then instead of seeing a popup chooser, the link just works to open the single topic.
Give that a go and see how well it may work.
Helpful and Handy Links
Thanks to you both for your responses. I have submitted a feature request.
Rick, were you suggesting to insert the Related topics button on top of the image map?
Mmm... as far as the image map is concerned, it seems that the conditional expression I tried using yesterday to no avail is now working (I made the <area/> tag conditional). I changed nothing in the meantime, all I did was close and reopen the project. No accounting for RoboHelp behaviour...
(Of course, this changes nothing to the conditional <title> tag issue.)