Well,
I was hoping some folks who actually know what they are talking about would have some useful suggestions for you by now.
I am so not an expert, or personally familiar with all the plants on your list...but looks to me that none of them absolutely require special rocks for their happiness, as in they could grow in a well drained scree just fine, which allows you a great deal of freedom in design and execution.
What rock material do you have available?
Is the mini-mountain for drainage or aesthetics or both?
How is your drainage? do I recall some seasonal flooding lake or something or am I getting people's places mixed up?
maybe its just my luck, but it occurs to me that as soon as you succeed with summer drought tolerant plants the rains could return...
How's your humidity--some plants that flourish in lean summer-dry soil in arid environments will literally melt in high humidity. (for example, Stachys lavandulifolia, or so I have read. I don't know about IN, but I used to live in MN and recall miserably humid summers. I planted one here this year, did great--I love it...but I never tried one in MN. I did have the monster byzantina at the MN farm, out on the badly neglected, wind tunnel, boulder pile, never watered--tough as nails, but even it had some issues with the humidity. I use byzantina here on the 'north 40' for erosion control on a steep drop to the road with no summer humidity evils, because this is a desert.)
Anyway--I have never grown mimulus because I don't think they could survive my winters, but I have a lot of penstemon, a few pulsatilla, and campanula...and a bunch of other stuff not on your list.
For me, here, on this part of the mountain, drainage is a key issue because I have serious clay that doesn't drain when it gets wet and it wont get wet (runoff) when it gets too dry. It is rare for me to see a worm so I don't really understand what the worm problem is. I have had to incorporate a lot of grit and organic matter just to grow anything, so that water can get in as well as move out. And in the areas where I have done that, things work pretty well. Plus, and, raising beds and using hills.
Still though, providing water--especially to establishing plants--can be a challenge. I have also erred on the extreme side and tried to plant some precious little things that demanded so called perfect drainage in pure sand/gravel and killed them because I failed to provide sufficient 'thunderstorms' during the epic heatwave--whereas same/similar plants in a soil mix survived. Go figure.
Winter is only just getting started...
I gotta go to bed
