Hmm. This is a tricky subject. Theme is definitely tied up with the storyform -- in fact you could probably say that in a way the storyform is the author's message!
I just meant that if you're trying to determine your storyform, it may or may not help to consider your theme. First off, you may find that as you develop your story and see it through the lens of Dramatica, that your theme may be a lot more complex than you initially thought. Also, the way you see your theme might relate directly to Dramatica story points and elements, but it might not.
Most people might get that the theme of Star Wars has to do with trusting in something, and that would certainly help you figure out the storyform. Same with The Matrix if you notice the problems with skepticism, not believing in one's self or in Morpheus's vision, and remember how Neo only comes into his power when "He is beginning to believe". For these stories, the Problem/Solution is quite clearly tied into what most people might see as the theme.
But take The Princess Bride; most people would guess that theme to be something along the lines of the power of true love -- "Death cannot stop true love." Yet I don't think that helps you figure out the storyform all that much, because that story's argument is more complex. It's not as simple as "have Faith in love", it has more to do with embracing the potential of true love, and not getting stuck in your wrong-headed evaluations of things. Something like "always consider love's great potential when evaluating your circumstances, and re-evaluate when necessary".
With my own story I thought the theme was all to do with promises and oaths because they show up everywhere, so when I tried to storyform it I tried so hard to make Obligation the OS Issue or at least MC Issue, but that never worked. (I was new to Dramatica then.) Only when I jettisoned that did I get the right storyform, and it turned out surprisingly (since I didn't select it) that Obligation was actually the RS Issue! And my theme is more complex than I thought; I think what I'm saying is that all these obligations are like chains and burdens (Crucial Element of Hinder).
As for your comments about changing concerns, I sort of operate on the principle that my subconscious has a particular storyform in mind for a story idea ... and what you want to do is align your storyform to that. So I think you should only consider changing concerns if you suspect the storyform you have isn't quite right, i.e. it doesn't match your story idea.
Unless you started with the storyform and started building the story from scratch using that, like is done in Story Embroidery sessions?