Change to "Wildcard" in GREP?

While it is possible to search for wildcards in Find/Change, (such as any letter or any digit), is it possible to change a character to a wildcard character?

My desire is to change each string of placeholder characters labeled ‘YYY XXXXXY’ into groups of random letters and numbers. Is this something InDesign is capable of?
For context purposes I am working on a project that is dealing with the naming of fictional exoplanets, which generally have names like “HD 72659b”, “YBP 1514b” and so forth. I am hoping to replicate this format.

Some exoplanets have less random names such as “Kepler 2b” as well. If there is a relatively easy way to draw from a string library in InDesign that would be lovely to know as well.

I am new to GREP, ID scripting and this community, so your kind help is appreciated immensely. Thanks for all your time guys.

Matt