With the understanding that...
Dm -> C -> Bm -> G -> A -> D
...is a series of key changes, and then reading this comment...
The G -> A -> D is the classic IV -> V -> I cadential progression.
...I think you maybe conflating standard chord progressions with key change sequences.
Consider this: a common template of key changes in classical style for a major key composition would be...
||: I V :||: ii vi I IV I :||
The middle area after the double bar can be different, but typically minor, you could abstract it to...
||: I V :||: ? I IV I :||
? being the development section in the textbook sonata plan.
Most of those key changes when viewed as chord progressions would be roots by descending 4th.
IV a descending 5th.
I an ascending 3rd.
Nothing horrible when viewed as a chord progression, but certainly
vi I isn't a strong progression and
I IV I is hardly an ending. Suffice to say I don't think the sequence of keys in that style depended on how they would work as a chord progression.
I will offer an alternate view. It doesn't come from a textbook. It's just my view on how I think that template worked as a common plan.
First let's distinguish two very important moves
I V a descending 4th and
V I a descending 5th. Two things so common we hardly think about them. The first is an opening. It creates an unrest, a forward impetus. The second is a closing. It creates a sense of repose and a conclusion. So we can say roots by descending 4th create forward impetus, descending fifths create repose.
If we return to the common plan, notice that the sequence of keys begins with opening moves which exploit forward impetus. The move
I IV the descending fifth is not used until the end. It's very sensible to place the forward impetus at the beginning and the repose near the end. Using the subdominant (the
IV) key at the end is so common in classical style, the feeling of relaxation so strong. I like thinking of that as the denouement which is borrowing a word from literature. This concept of opening lines followed by denouement is a kind of narrative view of the key changes.
Another way to view the plan of key changes is
IV are the tonal degrees of the key and as such are like the tonal pillars of musical architecture. The
vi areas are the modal degrees and drift away from the primary tonality. To complete the architectural metaphor you could call those middle minor keys the arch supported by the pillars. That middle arch region drifts away from the main key but it is contained or supported by two solid tonal pillars.
So on a large scale view of an entire movement we can understand the sequence of keys with a kind of narrative framework or an architecture metaphor. You could come up with other descriptions, but the main point is the key changes don't need to reflect common chord progressions like
IV V I. That clearly isn't fitting the standard classical plan.
Your design of key changes does not need to match up with a common classical plan. You can make your own design however you choose. But also you don't need to make it fit a chord progression. You can do that if you want, but it is not require by some kind of classical convention.
Regarding your key plan.
It's hard to say much about your key change design without knowing the details.
For example when you say it goes from
D Aeolian to Dorian - dropping the flat - and then a cadence on a
C chord. That suggests a kind of incomplete cadence and that surely would produce forward impetus. Seems good at the beginning.
You point out the
Bm change is a puzzle. But what happens as everything unfolds? Does any thematic material from
Bm get reintroduced in the final
D major area? That could provide an effect of resolution in the vein of a recapitulation.
Starting and ending on the same tonic
D certainly provides a traditional framing.
I'm just speculating. So much depends on the specific details.