There is indeed a actual way to implement a 15% Crit Boost of any class of your choice instead of the usual Swordmasters, Beserkers and Supertrainees.
If you don’t have FEBuilderGBA installed on your computer or laptop, I would suggest downloading it. It’s a really awesome tool, it’s also not complicated like Nightmare. Here’s the link to the tool.
Once you do get that done, open up the tool and with whatever FE GBA game you have. Click on the choice that says Open Rom, once you done doing that. It should open up the game’s inside goodies and choices to click on and mess around with, you should see Class Editor. Here’s a picture.
You click that and you should see all of the classes, click the class of choice and you’ll see a list of options to choose. In the bottom section, you’ll see Ability section. Ability 1 has Crit Boost, right in there. As you can see in this picture.
Press that check box and it’ll give that class an automatic 15% Crit Boost, but above 20 isnt an option. No ASM hack so far dedicates to a Crit Boost increase of choice. . . Yet? Maybe one day.
As for the second, well none have yet made a freeze as a status effect asm hack to add with the other status effects. Well maybe one day also, someone could make one.