Nothing's logical with WisDOT.
The Elm Rd interchange itself is not logical. I don't get what purpose it would serve. Elm Rd ends just to the west at 27th street and just to the east at 13th street. There is nothing of major significance on either side that would warrant an interchange. If Elm Rd went farther east to Howell Ave I would get it as there is a new industrial park being built there.
There's quite a number of businesses along 27th Street that likely counted on access that the original exit used to provide. And that area has been growing more and more. Having an interchange between 7 Mile Road and Ryan Road makes sense and putting one at Oakwood wasn't going to be easy.
Using Seven Mile Road interchange would have worked just fine.
Not really.
Why do you say that? It's less than a mile south of where the old interchange was. I don't see any reason why it couldn't be used for 27th street traffic.
Look at a map. It is completely inconvenient with the routing 27th Street takes there. Especially considering that growth is likely to continue to occur there. Getting the Elm St interchange built makes perfect sense.
The Seven Mile Road interchange is definitely not a suitable substitute for the former 27th Street one. For one, it involves winding around a busy two-lane frontage road, that gets very busy during the warmer months because of Seven Mile Fair.
It is only marked as WIS 241 because 27th Street becomes the west Frontage Rd., and that's already a state-maintained route anyway. Notice that WIS 241 actually ends just before the Seven Mile interchange, as the SB Frontage Rd. picks up again?
As for accessing 27th St, the new Elm Rd. exit is effective, and will become even more so as businesses start to build in that expanded area.