First off, I commend you on all the work you've made so far in providing the PSO community an update to the aging UI of this game.
Now, when it comes to specifics, ie. the R, I'd recommend providing the image(s) and instructions for those who want those preferences implemented. As a fellow artist, I suggest that you stick to your goal. You're always going to get "requests", at some point. Not everyone will understand that it's not only extra work, but a time-consuming process to provide these "alternatives"/changes. If you want to cater them, that's your call. Then you might find yourself feeling like this project had gone from a "labor of love" to just plain labor.
As for rendering tips, I'd zoom into the original file and render your vector image at that size, in reference to your sample trap icon. Then you can enlarge the vector to whatever size you need. The thing to watch out for is the thickness of your lines and have it scale accordingly. If you need a better explanation, I can provide you with an example; send me a DM.
I hate that Illustrator went subscription and I'm not a fan of Inkscape, it feels clumsy. I've since switched to Affinity Designer and I believe you can still try it out before you buy; worth the purchase. It's what I've been using when working on my own custom skin/mods to the game. Cheers!
*Also, I came across this page:
You can play PSOBB offline, to maybe help with testing things, without the need to jump online until your final edits.