Best of luck, whatever you decide!
Honestly, I think student-grade materials would work just fine; most of the acrylic paints I use on my PYO pieces are NOT expensive! ($0.85 – $1.50 range, so very cheap!) So far they’ve worked great. Haven’t had any bad reactions with the more expensive paints, or with mixing with other cheap brands. I did find that one cheap brand was much runnier than I was used to, but that just took a bit of practice to deal with; the paint itself was fine once I figured out I should use more layers to build up the color.
I suspect that cheap paint + good expensive sealer would be enough to preserve your piece for many many years. 😀 (Which reminds me, I need to go buy some matte sealer; I only have satin and gloss, and that won’t work for my winged wolf!)
If you do try the markers, I’d try them on the bottom of the piece, where they can be covered by the felt if needed. I’d worry that the alcohol or acid in the ink would mess up any paint put on top of it, either keeping it from sticking or altering the color over time… but I can’t be sure since I’ve never tried it.
Interested in buying or trading for: GB Pebble Sitting Red Fox in dark grey, Lap Dragon Test Paints (Water Sprite, Glacial Pearl, Opulence, Pastel Rainbow, and many others - see my Classifieds ad), Blue Morpho OW, GB Pebble Loaf dragons in blue/aqua/teal, and Griffin Test Paints (Black Rainbow or Frosted Jade).