I also fixed clothing sizes for my family using a hacker mindset, but in a different way:

Did you know that most professional sewing charts are just DXF files?

And did you know that DXF is the most common file format for laser cutters?

;)

=> just let the machine cut out precisely the clothing shapes that you need

After a few tries, I also started to add small sideways cuts to the outlines as alignment markers. And then you just need to connect the pieces where you marked them while always leaving roughly 0.5 cm of gap to the laser cut line. I went with 0.5 because my sewing machine has a hardware alignment guide with that offset. And at that point, it takes a skilled tailor only mere minutes to finish a shirt, which means in exchange for their 1x hourly rate they will be willing to finish off 5x proto t-shirts for you.