Putting aside subjective and inherently flawed standards of physical beauty...
The OP does touch on a thought that I had.
Why are Inquisition's LI offerings so starkly unbalanced across gender preferences? Past games didn't have a problem with keeping a balance with the available love interests, so why was this outright abandoned for Inquisition?
The only thing that I can think of is that this was intentionally done for political reasons (sticking it to entitled straight male players (Gaider's comments reinforce this idea even more)) and as a response to the unbalanced treatment of Love Interests in Mass Effect 3 (Namely that Female Shepard was screwed with Male Shepard basically having his own Harem by comparison).
But for what purpose? There really isn't any reason to abandon the LI balance that's been maintained through the series unless the developers intentionally wanted to inconvenience the players because...they could.
I'd put in the same category as asking why the developers wanted to introduce race-gates to romance arcs when there's no benefit that comes out of it that you don't already have. It was put in because the developers wanted to put it in.
To directly answer the OP, another bisexual option in the form of a female character similar to Isabella would be good. And this is from someone who likes all of the LI's despite confusion and mistrust about the developers intentions and mindsets when determining Love Interest Availability.