Ralf, you may have a few options.
Option 1. Since your lpstat -a returns both printers, then instead of needing to go into the cups web interface each time to re-direct, you might be able to go into your terminal and do:
lpmove EPSON_R285 RAW_R285
I don't know if you only need to do this once, or every time you try to print. If you need to do it every time, in terminal you can use your curser arrow keys (up) to recall previous commands making it simple to redo, that may be your simpliest option.
Or you could write a script, with nano or vi or some text editor, something like:
string=`lpstat -o EPSON_R285`
if [ -n "$string" ]
lpmove EPSON_R285 RAW_R285
If you don't know how to do this, in terminal, you can "nano movejobs" then type/paste in the above, write it out, exit nano, then in terminal "chmod +x movejobs" and then "./movejobs"
If you shut down, you will again need to "./movejobs"after starting up each time. Every minute, it will check if your queue for EPSON_R285 has anything in it, and if it does, it will move it to RAW_R285. I don't have the same problem as you, so I haven't tested this.
Option 2. To get CUPS 1.6 and Mountain Lion to automatically work "Bonjour" with an older CUPS server, you not only need to change protocol to dnssd, but also according to what I have been told on the cups forum, 'use one of the various add-ons to register DNS services for each of the queues so they appear in the "nearby printers" list.' If anyone else is reading this and understands this, please help me out! I have gone to the cups forum, created a login and expressed some of my frustration.
Option 3. I seem to have my system again working by doing this: I go to my MBA running Mountain Lion, safari > localhost:631 (this is the cups web interface) then click on the admin tab , click on "Add Printer" button, I selected "Internet Printing Protocol (ipp)", next page in the connection box I entered "ipp://192.168.1.104:631/printers/MP160", next page I fill in Name, Description, Location, I do not check "share this printer", next page, for the "make", there wasn't cannon available, so I selected "Raw", next page under Model, "Raw Queue (en)" was all there was, so I clicked "add printer", next page was banners, I left it to none, and clicked "set default options". This seemed to set it, it told me default options have been set successfully. Now when go to "System Preferences" > "Print & Scan", the MP160 shows up as kind "Remote Printer" I hope what this means is that my MBA sends the pdf file to the server and then it gets printed using the driver on the server (linux running cups 1.4). It seems to work for me, even after rebooting, but I can't guarantee it will work for you. I could not get adding the printer using OSX "System Preferences" > "Print & Scan" > "+" to work, no matter how I filled it out.
Eventually, I may try installing CUPS 1.6 on my linux.