I don't see this mentioned anywhere here, but there's a website I came across years ago that allows you to do the same, but you just scan the sheet instead of mailing.

https://www.calligraphr.com/en/

Albeit it's not entirely free (pricewise or otherwise). I still think your second idea is better, where a learning algorithm "captures" handwriting and generates a font or more text with the same style. I can only imagine the implications in authenticity and forgery, though.

I came across that in 2005s, & obviously could not pay that much; so searched around for free ways to do that. Found an article which listed to download that your website's grid; write with a thick pen; scan & then use FontForge to convert it to a font. Lot of labour. But I did it; & still have that font; used on many paper forms.

Now recently few years ago I came across an app where you draw each letter on mobile; then it sends all data to its server & you get the font. It worked for few months, I made few variations of my handwriting, then its server stopped responding.

Now I have another font where few glyphs of my signatures (few variations), my logo, my initials are as font; & I use it to sign checks or forms or such.

In the mid-2000's I got a Toshiba Portégé convertible laptop off eBay for a few hundred bucks. It had an active digitizer built in and had some software that let you do something similar. It wasn't fancy enough to include alternates and it wasn't the best at connecting cursive, but if you mainly used print/non-script letters like I do, it was a neat trick to be able to use some semblance of my handwriting as a font in Windows.

Probably this Windows XP Tablet PC Edition Power Toy: https://www.gottabemobile.com/8220my-font-tool8221-tablet-pc...

Yep. That was it!