> If the nine Indic scripts were isomorphic, a single keyboard would have
> served for all of them.
FWIW, Unicode doesn't treat the Indic scripts as isomorphic. It
follows ISCII in laying out the main Indic scripts in a parallel
fashion, leaving holes and gaps as needed for places where one script
lacks a character found in one of the others. ISCII did it because
they thought it would ease transliteration between the various Indic
scripts. Unicode does it because its practice at the time was to
follow as far as possible extant government standards. There is
certainly no expectation that the precise details of how to render the
Indic scripts are the same; indeed, Unicode attempts to provide
separately for each Indic script the details on its rendering.
(Although that sometimes amounts to saying "Script X is rendered like
script Y with the following exceptions…")