[Ian Grant]

Hmm. Why does the formula call for citric acid? Do you think I could subsitute Ascorbic Acid for the Hydroquinone, making a p-Aminophenol/Vit C warm tone paper developer?

Citric Acid is used in quite a few warm tone developers, so must serve a purpose so adding Ascorbic instead would probably have the wrong & possibly an opposite effect.

My Bible (L.P. Clerc) is still in the UK as it's rather heavy but I think he'd explain why it's used.

That high level of sulfite and high level of bromide might do some nasty things to modern chloride papers. IDK for sure, but I would suggest a test first. It would certainly be good with Bromide or Br/I materials.
PE

Once diluted the levels of Sulphite &b Bromide are more typical of other developers.

Ian