Someone named novoid on GitHub suggested to add some flexibility to the 
ASCII bar plot.
Attached is a patch implementing it.

Example:

| 1 | WWW          |
| 2 | WWWWWW       |
| 3 | WWWWWWWWW    |
| 4 | WWWWWWWWWWWW |
#+TBLFM: $2='(orgtbl-ascii-draw $1 0 @>$1 12)

Note the @>$1 cell reference passed to the MAX parameter.
Previously, only hard coded values like 4 could be used.

Regards
Thierry