The minimal requirements for a generator are:
<p>
<ul>

<li> the footprint family is a series of footprints that can be generated 
using the same code, with changing some base properties (e.g. number of 
pins)

<li> dimensions and other properties can be calculated from the base 
properties with reasonable formulas and conditional code; e.g. sot* is not 
a good candidate for generation, as sot23 or sot89 can not be generated 
from some common ancestor by varying one or two parameters, but would need 
a large table that translates package name to a pattern - easier to keep 
those in static footprint files

<li> has a reasonable amount of existing variations; e.g. it is not worth 
writing a generator for the dsub family because there are only a few of 
them in common use (db9, db15, db25, and maybe db37).

<li> preferably a link to a datasheet that shows at least 3 members of the 
family; if that's not possible, separate datasheets describing at least 3 
members of the family.

</ul>