Yes, you can certainly remove and store our refillable carts with ink inside. To do this, we recommend storing them in sealed zip lock bags to prevent drying.
What profiles are you using with our ConeColor Pro inks? What papers are you printing on? Epson pigment ink contains some dye to help improve color vibrancy and gloss compatibility. Our ConeColor Pro inks are pure pigment, and specially formulated for the best color output, compatibility with a wide range of media, and good flow in a variety of Epson printer models. Ink chemistry isn't as simple as pouring things together, in doing so you completely change the chemical makeup of the inks in ways we can't possibly know of or support. People experiment all the time, so you can certainly try your hand in ink chemistry, but please be aware that we can not support you in this experiment, nor offer you any information in regards to how this mixture will work, the longevity, etc...
Best regards and happy printing~ Dana