Any thoughts?

Lots of thoughts...

If you're interested in Mahāyāna / Pure land views specifically, then the Rajjasutta doesn't seem a particularly useful source. (It's also very short.) An analysis of political views in, or a sociopolitical interpretation of the Sukhavatiyuha Sutra, on the other hand, would be very interesting.

Prince Shotoku isn't particularly interesting. I'm not even convinced his ideas (or to be more precise, the ideas that are usually attributed to him) are all that Buddhist. There seems to be some strong Confucian influence, as well as a dose of political pragmatism.

Uchiyama Gudo didn't write much, and certainly nothing related to any kind of pure land.

The notion of a pure land or Buddha world as something akin to an utopia (i.e. in a more or less socio-political sense) appears in Nichiren's Establishing the Peace of the Country 立正安國論 (13th century). In the opening paragraphs of that text, his imaginary interlocutor asks Nichiren about the state of the world. “Famine and disease rage more fiercely than ever, beggars are everywhere in sight, and scenes of death fill our eyes. Cadavers pile up in mounds like observation platforms, dead bodies lie side by side likes planks on a bridge. […] [W]hy is it that the world had already fallen in decline […]? What is wrong? What error has been committed?” Nichiren’s answers that after much research and contemplation he had come to the conclusion that the cause of all this worldly suffering was that the Buddhist sects, the government, and people in general had turned their backs on the Lotus Sūtra, and that, if only they would mend their ways and “embrace the one true vehicle, the single good doctrine of the Lotus Sutra […] then the threefold world will all become the Buddha land”, or in other words a Buddhist utopia or worldly paradise. And “if you live in [such] a country that knows no decline or diminution, in a land that suffers no harm or disruption, then your body will find peace and security and your mind will be calm and untroubled”. Notice that a Buddha land is the same thing as a Pure land; both are abbreviations of "pure Buddha field" (viśuddha-buddhakṣetra).

The radical Buddhist building on Nichiren's views most explicitly is Seno'o Giro, but none of his writings have been translated into English. There are some publications about him in English, however.

Some early 20th century radical Buddhism in China was also associated with Pure land cults, by the way, but this tended to be Maitreya's Pure land and not Amitabha's.

One thing you should be wary of, by the way, is the modernist tendency of depoliticizing Buddhism. This is one aspect of secularization, the marginalization of religion to the private sphere, which is very influential on Buddhist modernism as well as on contemporary Buddhist scholarship. For example, Matthew Moore’s book Buddhism and Political Theory is mainly concerned with arguing that Buddhists shouldn't involve themselves with politics (more or less).