No offense at all to Elrhamlin, but -- as someone who did computer game design many ages ago and who spent many, many years designing commercial software in general -- I read posts like this (there are several others in this sub-forum) and sigh.
Do you really not understand the very real tradeoffs of time and complexity that every single feature presents in developing software? Let's take the suggestion above. Yes, FE already has a unit-design subsystem. But look at it carefully: as currently implemented, it's intended to design pretty much a single humanoid shape, with appropriate weapons, armor, clothes, humanoid characteristics, etc.
Now let's open the door for all 'forest drakes and other monsters'. It would seem to be a natural and straightforward extension. But here are some of the immediate issues:
-- First, what are you going to allow the user to do? Change color? Appearance? Basic stats (old or new)? Traits? Size (something not an issue for the humanoids)?
-- Second, what are the possible destabilizing or unbalancing effects? How do you set this up so that the user can't create a killer drake that AIs just can't cope with, at least, not at a point where the user hasn't progressed sufficiently up the tech tree? In other words, what does it really add to the game design and balance, and what does it take away?
-- Third, how much work -- UI design, art work, actual function implementation, etc. -- will be required to implement all this? And we're not just talking the artwork in the design panel (though that's not trivial at all) but also the artwork and animation for these custom creatures within the game. (I strongly suspect the underlying game/animation engine handles this well, but it's still actual time and work. Everything takes actual time and work.)
-- Fourth, what new bugs or issues will be introduced as a result? It is well known in software engineering that simply fixing a known bug has a real, measurable probability of introducing a new one; for new features, the probability is a certainty, and it will likely be more than 'one' new bug.
-- Fifth, what other features/bug fixes are going to neglected in order to design, implement, and test this feature? Because there really is no such thing as a free lunch, especially in software development. Much of software development -- at least, the successful kind -- is throwing out features, some of which are truly wonderful, because without that ruthlessness, you just won't ever ship (or you'll ship so late that no one will ever care).
So, yeah, I think the lack of custom design of monsters is very intentional. I'm sure it's bubbled up at some point in internal FE discussions and was given a particular priority, ranging from "in the next beta" to "when hell freezes over".
But that's just my $0.02 worth. ..bruce..