I read over this topic again this morning, and my response. I think I should try to explain a bit more. Obviously, what I am recommending is not a "forest" as such, and is more of an arboretum, or collection of specimen trees/groups to create a beautiful "artificial" area of trees.
What you say you want is to create a "natural forest," much like some of the more "open" forests you see in your part of Michigan. By the way, I studied forestry at Michigan State University, many, many, many years ago, and spent a lot of time in woodlands there both as a part of my studies and for pleasure.
Establishing "forest" from "scratch" with planted trees is very difficult and time consuming. It is easiest with pines or other conifers, and if there is to be a variety of species, they must grow well together at similar rates. Initial spacings vary from 6 to as much as 12 feet or more, depending on the species. With Norway spruce, initial spacings of 6 feet will lead to the best final results, because with many seed sources, there is great variability, and the more opportunities there are to thin for the best trees, the more very fine individuals will be in the final stand. with red pine, there is not the same advantage with close spacing. With white pines, the advantages of closer spacing are between the two.
But, the bottom line is, even with conifers, to create a beautiful forest relatively quickly, one must put in a great amount of work, both thinning and pruning. An un-pruned and un-thinned stand of white pine, for example, after thirty years can be a very, very unattractive thing in the eyes of most people. If the trees are planted 20 feet apart to reduce the need for thinning, they will be limby, and may not grow straight and tall. If they are pruned regularly, and the leaders are tended to as others have suggested, the result can be OK, but you won't get so much the "cathedral" effect that is so wonderful with white pines.
With a stand of mixed hardwoods, the problems are exponentially more difficult. Without using very careful methods, including planting much closer together with an eye to later thinning, as Joe, and PA Wilderness, etc. have suggested, ending up with a forest anything like what you envision will be almost impossible. If it were possible, it would be so only with very regular and careful pruning, and "leader tending"--a huge, huge amount of work.
I mentioned in my original response that the compatibility of the trees growing together is a difficult issue. One must be very careful not to plant a slower growing tree next to a substantially faster growing tree, or it will be overtopped, suppressed, and lost. And which trees are compatible varies by site--some trees grow much faster on wet sites than dry ones, and soil types also matter. And growth forms matter. Some hardwoods that eventually grow broad crowns start with a more narrow conical crown. Trees that grow this way can be planted near each other. Other trees when young will spread more, with branches arching outward. Maybe these should not be planted next to those starting out more narrowly. Trees with very good shade tolerance, such as sugar maples are more resistant to "competition" from nearby trees, and can grow nicely between taller trees. Other trees, unless they have a 90% or more angle to the open sky, will have their growth retarded.
So, what I am trying to explain here, is that deciding which trees to plant near other trees can be a very complicated job, especially if you are including a large number of different species. Working all this out could be a fun pastime, but unless you are expert in such matters, it is easy to make mistakes.
So, with all that I have tried to explain here, I would encourage you to go with an "arboretum-like" plan, something like what I have suggested in my original post. AND, there is the issue of TIME. Even if you could establish artificially the kind of forest you envision, it won't look like much in less than 40 years, and to be like the forests you see in Michigan, will take at least 70 years or more.
So, in all good conscience, I must recommend the "arboretum" kind of plan I suggested. On another discussion forum elsewhere, a number of years ago, I tried to advise someone, at great, great length, on how to artificially create a mixed forest of hardwoods and conifers. I spent a lot of time trying to describe how this "could" be done. I repeatedly said that I thought it extremely difficult, but the individual was completely determined to try. I now think I did a disservice by going along and giving all the advice I did. Efforts continued for a few years, and then they were given up, time, and efforts wasted, and hopes dashed.
I would hate to have you put in a lot of effort and have it come to little or nothing of special value in the end.
I will close with a comment about spacing in a mature natural hardwood forest. 25 feet for hardwoods may be too close, depending somewhat on species and site quality. A fine stand of white oak on a very good growing site will have trees at an average spacing of 30 feet or more. I have a nice young (48 year-old, 95 feet tall) stand of white pines on my timberland, and their spacing is already fairly tight at about 20 to 25 feet. Of course there are lots of variables.