I don’t think Reagan had any input at all in the choice of the convention in Detroit; it was made by the Bill Brock people, and I know Brock was once “conservative” to a degree.
I'm still baffled why the GOP selected Detriot in 1980, it seems a bit like the RATs deciding to hold their convention in Myrtle Beach, SC.
Even though it was 34 years ago, I think by 1980, Detroit would have had a similar reputation as it has now, as a RAT-infested cesspool. If the point of the convention was indeed to be a "symbolic" representation of how the Carter administration was taking America in the same direction as Detriot, it seems to have worked.
Of course, in that respect, it makes equal sense to have it in Cleveland in 2016:
http://www.citymayors.com/gratis/us_cities_shrinking.html
Cleveland isn't the crime-ridden hellhole that Detroit is, of course (there are a number of popular tourist attractions like the Rock & Roll Hall of Fame, as well a very picturesque historic area called the Tremont neighborhood), but the city's population decline and stagnant economic situation is similar.
Fieldmarshaldj's suggestion makes more sense for an Ohio showdown though: having the RATs meet in Cleveland and the GOP meet in Cincinnati.