Let us expand the idea of two-sided (from the analytic/synthetic duality standpoint) grammatical analysis: consider, for example, ‘beaucoup et souvent’ (a lot and often) in the sentence ‘il mange beaucoup et souvent’ (he eats a lot and often). Analytically, ‘beaucoup et souvent’ is composed of and adverb (‘beaucoup’, a conjunction (‘et’) and another adverb (‘souvent’). But synthetically, ‘beaucoup et souvent’ is an adverb, the structure of which is ADVERB+CONJUNCTIONCORD+ADVERB, according to the meta-rule ADVERB = ADVERB+CONJUNCTIONCORD+ADVERB . In the same way, ‘beaucoup mais souvent’ (a lot but often) is also, from a synthetic point of view, an adverb. Analogously, ‘rarement ou souvent’ (rarely or often) is also an adverb, from a synthetic viewpoint. In the same way, ‘rarement voire jamais’ is also a synthetic adverb. This leads to considering ‘even’ as a conjunction of coordination.
Now it is patent that we can expand on that. As hinted at earlier, it seems some progress in rule-based machine translation (we should better speak of, say, ‘human-like MT, since it mimics human reasoning) requires revolutionizing grammar.