Jon -- I started a new topic as the last one seems to have dropped some posts and I wanted to make sure you got this.
I spoke with Wells yesterday about doing what you suggested, i.e. replacing the old ink ink with fresh ink.
After replacing the ink, one cartridge wouldn't reset, so I replaced the chip from a set of fresh empty cartridges I was saving to do a piezoflush if needed. It reset correctly.
Now am having trouble as the printer erratically sees the entire left bank of cartridges as missing.
Here's how that developed:
After refilling the cartridges yesterday, it failed to see the left bank of cartridges. I thought this might have to do with the cartridges being a bit damp after refilling (I had wiped them completely dry, but worried they might have contained some dampness from the re-filling). I left them out overnight and this morning they seemed to be bone dry. I put them in the printer and, "Hooray!" it fired and read all the cartridges, Then I shut it down and re-started in Service Mode to do an initial refill (per your plan) and it no longer recognized the entire left bank of cartridges.
I checked the chips and they all reset to green.
Going back to a regular (not Service Mode) startup, it still does not see the cartridges.
I am expecting an Epson guy soon to replace the dampers and I don't want to be dealing with a "third party" inking issue when he comes.