@Kanorin
Interesting list, some good ones on the list. I went through the list, because I could order and have them ship to my sister in Saint Louis. I might put in an order, have not decided. Made some notes for myself, but I thought I'd share, maybe save you some time. All the oaks have the same problem. They are slow to get to the point where their leaves are small enough to consider putting them in a mixed planting.
Taxodium disticha - bald cypress - good as single species forest. Difficult to mix species with it, except maybe button bush - Cephalanthus occidentalis - comes from same flooded habitats as bald cypress, will grow well submerged for part of the year.
Cephalanthus occidentalis - buttonbush. Leaves are small enough, it could be used in mixed forest plantings. It tolerates wet soils. It can survive with roots flooded for most of the year. But it does not need its roots flooded.
Rhus aromatica - aromatic sumac - so far has proved "pretty okay" for bonsai, but I'm only 3 years from seed. Small enough leaves. Probably good for a mixed forest.
Nyssa sylvatica - black gum - in theory great for bonsai - in practice there are issues, all who have reported had trouble. Maybe a bad choice for mixed species forests. But might work, little is known.
Ilex serrulata - deciduous holly - excellent for bonsai, small leaves, beautiful winter berries, but must have a male somewhere within 50 feet to ensure pollination. Good for mixed species forests.
Quercus macrocarpa - Bur Oak and Quercus velutina - Black oak - and other oaks on the list; all have large leaves, that do eventually reduce, but probably not good for mixed species forests.
Crataegus viridis - Green Hawthorn - seedlings should work well in a mixed forest. Certainly good for individual bonsai
Celtis occidentalis & laevis - Hackberry - both species of hackberry are good for mixed forests and good as individual tree bonsai
Picea abies - Norway spruce - not a Missouri native, but could be used in a mixed species forest. Has a good track record as bonsai.
Maclura pomifera - Osage orange - leaves are small enough can be worked into a mixed forest. Only allow fruit on largest of individual specimen bonsai. Jim Lewis, RIP, had some decent Osage orange bonsai.
Diospyros virginiana - Persimmon - leaves are big, but reduce well, a bit touchy about how roots are handled, but could be worked into a mixed forest, at least in theory. Good for medium to large bonsai as individual specimens.
Pinus (rigida x taeda) hybrid pine - might be good, might be too vigorous.
Amelanchier arborea - Service berry - definitely good for a mixed forest. Good as individual bonsai, good for smaller size bonsai. Slow to develop trunk caliper. Lovely white flowers before leaves in spring.
Pinus echinata - shortleaf pine - this pine sounds really interesting to try out as bonsai. Probably best as individual species forest, rather than mixed forest.
Spicebush - Lindera benzoin - K Murata had a lovely Japanese Lindera forest, the USA species should be as good. Leaves are on large size, but reduce well. superficially similar to persimmon leaves.
Washington hawthorn - Crataegus phaenopyrum - excellent as bonsai, individual or single species forest. Should be able to work it into a mixed forest.
White Fringe Tree - Chionanthus virginicus - bad choice for bonsai, bad choice for forest - from my personal experience. Branching too coarse. leaves too large and don't reduce.
Wild Plum - Prunus sp, - excellent for bonsai - mixed forest may be possible. Flowers before leaves in spring.
Witch hazel - Hamamelis vernalis Spring or late winter witch hazel - and Hamamelis virginiana - autumn or winter flowering witch hazel. - both species have leaves on large size. Might be difficult to work into a mixed forest. Both are good for a single species forest.