Very good discussion so far.
I'm in the camp of leaving the I-894 designation. Even though it is subsumed by I-41, it is still well known to travelers as the Milwaukee bypass highway.
What is needed along the corridor are better signage for control cities to guide people along the bypass. This should be done on the big green signs along the highways and at the three key interchanges that I-894 passes through. This should also be done at the cross street on-ramps, where now al you have are small roadsign signs for 41N/43S/894W ro 41S/43N/894E. At a moment's notice, it will be hard to keep up with this, especially given the confusion of the wrong-way 41/43 multiplex.
The signs at the Zoo Interchange seem very good, as they list all apppropriate highways. (All pointing south). The proper signs also put in "Bypass" (although my preference would be "Milwaukee Bypass") and have an airport symbol. Most importantly, Chicago is the control.
The stretch between Zoo and 43 should have control cities signed from cross-street on-ramps. Southbound should be Chicago. Northbound should be both Madison and Fond du Lac. (Madison is the primary control where there is only room for one). 894 should be signed north/south on this section, not east/west.
The signs at the 43 interchange should have 41 south, 43 north, and 894 east for one direction and 41/894/45 north in the other direction. The signs for 41S/43N/894E should also include an airplane logo. The control city for 41S/43N/894E is properly Chicago if coming from the direction of Zoo, but it should list both Chicago and Milwaukee if coming from 43 NB. The control cities for 41/894/45 north are properly listed as Fond du Lac and Madison, but the controls need to be listed on signs coming from the airport as well. (The signs are only seen when coming from 43 N.)
The stretch between the Airport Interchange and 43 should have control cities signed from cross-street on-ramps. Eastbound should be Milwaukee and Chicago, with Milwaukee as the primary control. Westbound should be both Madison and Beloit. (Madison is the primary control where there is only room for one). The control cities are really important here as each of the three highways signed has a different compass direction.
Finally, at the Airport interchange, care must be taken that each highway have a cardinal direction posted. The controlled cities as currently signed here seem appropriate (Beloit signed on the exit from 94 EB and Fond du Lac/Madison signed on the exit from 94 WB). The only thing I would add are signs for "BYPASS" (or "Milwauikee Bypass") in a similar manner as signed from the Zoo Interchange.