I made aware of this due previous discussions on P-C but your comment here is very valuable. I hope to see your comments on other parts and aspects of it. For example is there something I've missed on web font difference with a print font? That would be very necessary for font designers as they usually designs print font rather than web suitable font.
But about italic, I completely understand your concerns but the problem is on Persian Wikipedia, users already used Italic widely I'd guess relied to it. The slanted/oblique/italic style is just something that is indicated on
manual of style and its already use-cases are not simply replaceable other style. Lake of correct oblique also had made some problems for example we are forced to automatically put a NBSP before articles titles that MoS indicates must have italic style, compare
this with
this. Also due some bug on current our MediaWiki PDF renderer we must build italic version of our print font for its use. So having a italic (which called oblique on the most popular font on Persian TeX community,
XB Zar) version of the web font is somehow needed for us even the fact it is something incorrect on Perso-Arabic script.
Using "shikasteh" is also interesting offer and actually I've linked you comment about it on that page already. Recently I saw on "Jameel Noori Nastaliq" the italic variant of the font was actually equivalent to "Jameel Noori Kasheeda". That was surprising for me at first but now is understandable. Thank you