Chromatic customization?

File near the base (rivet end) to tune down.
You can buy a nice tremolo harp already tuned for $100. About the same as $3 per reed on the retune (32 reeds). If you like doing that kind of work, then go for it. I once retuned a Suzuki in Asian tuning to a German Richter tuning. The Suzuki had dry (slow) tremolo and equal temperament. In Richter it became wet (faster) tremolo and just intonation (some notes a bit flat but nicer sounding chords, like a Hohner Echo harp). It was a success. Both reeds of an A note had to be retuned down to G, a whole step. You are only going down a half step. Other reeds were tuned just a bit. All 21 notes and most of the 42 reeds had to be adjusted. It was very time consuming. A Dremel tool helped speed things up. I had two of the same Suzuki in C because I found them online at a great price, $35 each. So one became a "Suzuki Echo Harp". I probably wouldn't do that again. I could have worked a part time job and bought 3 harmonicas for the time invested in that experiment! I have touched up the tuning on a few notes on several of my tremolo harps. That was well worth the time. A small amount of time invested for a large improvement in sound.
You do not have to remove the reed plates to tune the inside reeds. You can work through the slots if you slide a thin piece of metal through the slot for support.
Here is a video I made about tuning tremolo harps:
www.youtube.com/watch?v=Wr8azN7D1ps
In the description there are links to videos that are about how to tune a reed. I don't go into that a lot because the other videos described that process well.