There's nothing built-in other than absolute and relative line numbers, and it would be difficult to square a different addressing scheme with the numerical [count]
prefixes to the Vim motions. However, plugins like EasyMotion and vim-seek implement such, though for motions like the built-in f
inside a line.
For implementation tips, have a look at the RltvNmbr.vim plugin; it uses the sign column to emulate the now built-in relative numbering. As the sign column is two characters wide (and can display arbitrary characters), this would be fitting. That would take care of the visualization... you'd then only need a custom mapping to query for the Base26 line number, and translate that back into a jump.