Even if the English Wiktionary community would change to have per-language pages instead of the current system, it would be rather unlikely that all other language editions of Wiktionary would follow in a timely manner. I would prefer to leave this decision to the autonomy of the projects, and instead adapt to them (which is, by the way, what the proposal does).

Yair, as Daniel said, the current Wiktionary pages would not be mapped to Q-Items. Since this was unclear, I tried to update the text to make it clearer. Let me know if it is still confusing.

I do not think a separate Wikibase instance would be needed to provide the data for Wiktionary. I think this can and should be done on Wikidata. But as said by Milos and pointed out by Gerard, lexical knowledge does indeed require a different data schema. This is why the proposal introduces new entity types for lexemes, forms, and senses. The data model is mostly based on lexical ontologies that we surveyed, like LEMON and others.