Find/Replace Coding to Formatting

Twice a year I put together an approximately 1500-page document from an Excel spreadsheet. I code the information in Excel so that I can Find/Replace codes to paragraph tags, and then I save to tab-delimited text, clean it up in NoteTab, and bring the txt file into Frame. I've tried using Indesign, but Frame is faster (still slow with 1500 pages, but much faster than Indesign). I search for my codes and replace them with paragraph tags. I can usually get the tagging part done in about 15 minutes.

What's giving me agita is the character-level formatting (new this year). It's easy enough for me to surround the characters I want formatted with codes (like <italicon>italic words here<italicoff>), but I haven't found a way in Frame to easily Find/Replace this to a character format. This year I brought the text into Indesign, found and tagged my italics with a GREP search, and then copied and pasted RTF into Frame. This sort of worked. Indesign was really, really slow, and it left some phantom characters right before returns that made searching for returns in Frame impossible, but it was better than manually swiping and applying a format 6000 times (4 times per page).

There must be a better way. I'm using Frame 9. Did Adobe improve Frame's Find/Replace with Frame 10 (like, maybe, including GREP)? Is there a simple way to include markup in the text file? I don't need to bother marking everything up. The paragraph tags are easy enough to Find/Replace. ISTR something called MML that I played around with about 15 years ago, but I don't see it as a choice for Save As or for Import. I tried Saving to MIF, but it looks very complicated. Can I code just the italics in MIF and do the rest of the formatting in Frame? Or is there a better way?