Your questions always demand a bit of SF rigor. Quite right about the word class... I was blinded from above... manner degree so adverb... but mere/merely : adjective/adverb. …
And you’re right about gradability... in this context is it a judgement of capacity? Construing a series... a lowly scullery maid – mere housemaid – capable housekeeper
Blogger Comments:
[1] This is the topic sentence ("hyper-Theme"), with 'rigour' being Rose's evaluation of what follows.
[2] To be clear, the meaning of 'mere(ly)' is interpersonal (counter-expectancy: limiting), not experiential (manner: degree). For example, in he merely said it wasn't cooked properly, the Adjunct merely is not circumstantial: it does not qualify the manner in which he said it.
[3] Clearly, 'a mere housemaid' is not a judgement of the capacity of a servant. Mere housemaids may be more capable or less capable. In terms of APPRAISAL, it might be seen as a negative appreciation of the status of 'housemaid' in terms of social value:
But the fact that I’d sort of gone from that status position down to merely a housemaid, you know?