Arthur Greenwood wasn't a vigorous or dynamic personality but could, I think, do a decent enough job under the right circumstances. His "speak for England" episode was very much the exception to his personal style but showed he had inner steel, if not perhaps the confidence or opportunity to show it. I see him as a unity candidate - personable, inoffensive, holding things steady, reliably conventional. Think !2009Alan Johnson for the best modern comparison.
I don't really know enough about him personally to know his personal politics. I assume he'd govern under whatever manifesto he was elected under and a broad continuity of thought leaders, Beveridge, Keynes, et. al. Certainly much the same issues of shifting from a wartime to peacetime economy, decolonisation, war debts, and the wider sense of making the most of Labour's third government and achieving what Lloyd George hadn't after the end of the First World War.
Greenwood first stood for the Labour leadership in 1935 against Attlee and Morrison, where it was alledged (by Morrison and his backer Hugh Dalton) that Greenwood was the beneficiary of anti-Morrisonian votes for those not yet enamoured with Attlee, who at this stage was seen as a stopgag -and before then, a dull, pretty insignificant backbencher who by sheer luck survived the catastrophe of 1931. We know how very wrong that view was, but it does show that Greenwood was considered the best Stop Morrison candidate of the (admittedly reduced) intake of 1935.
As Deputy Leader for 10 years under Attlee, who was never in the best of personal health, Greenwood continued with this Stop Morrison credibility, and this is really the best chance for him, I think. He didn't have the depth of skill to rise to the very top, but, as shown by his Speaking for England and his tough line against negotiating with Nazi Germany in May 1940, when pressed he was something to behold.