They would just represent the party.
Look at the latest appointments... Schatz from Hawaii has just completely sold himself to the party as soon as he got there (granted, it was for campaign cash)
I take your point but governors like Christie aren’t going to appoint conservatives and it’s also subject to backroom deals being done i.e one party gets a senate seat, the other gets the 2nd and you let my bill/reform get through the State house.
Also the kinds of people you find appointed will be the most corrupt and worse people in the state like former majority whip’s and speaker of state houses...
Governors did not appoint Senators prior to the 17th, they were elected by state legislators. State legislators are elected by the voters in their states. It was a very wise system that preserved the interests of the states at the federal level. Which is why the 1900’s progressives did away with it. 1900s progressives wanted an all powerful federal government, like we have now.