I don't see your two issues as a reason for replacing roses. Most of the roses people want have thorns. Mildew isn't a big problem compared to others.
People replace roses because they are bored with them, they aren't performing well or are diseased. If you like what you have why go to all the work of replacing them.

Are you looking for roses that don't require any spraying? Some people use cloud cover to fight mildew.

I'm sure other posters will be abe to provide recommendations for thornless or mildew resistant roses.

Hi Grambu, .............. and I suggested you post here for more input ........... I wondered how deep your pots are. I had 'French Lace' in a 5 gallon pot tooo long.

Hope you get some florib. recommendations.