I’m not very good with feature code, but a glyph can be substituted multiple times, right? I don’t understand why rvrn can’t be used with non-encoded glyphs. Could you not simply write rvrn: sub a by a.italic and then ss01: sub a.italic by a.italic.ss01?
rlig and rclt are not always supported in Adobe apps. Only rvrn has universal support in my tests:
Illustrator 26
rclt 
rlig
rvrn 
InDesign 17
rclt
rlig
rvrn
Photoshop 23
rclt
rlig
rvrn
Chrome 100
rclt
rlig
rvrn
Safari 15.3
rclt
rlig
rvrn
Firefox 99
rclt
rlig
rvrn