For what it's worth, I did spend a bit of time looking at some articles about new high temperature resins. If things have to be made, then I'm keen on making them from composites if it's practical. Bismaleimide resins looks like the most promising in terms of price/performance/practicality. It is important to understand, I think, that there can be a big difference between the highest temperature a polymer can withstand, and the temperature that it can withstand on a prolonged basis, with repeated heating and cooling cycles. For example, here's a quote from a short 2014 piece on compositesworld.com .
"Toho Tenax Co. Ltd. (Tokyo, Japan) [...], announced on Nov. 6 its development of a new prepreg that offers super-high-heat and oxidation resistance, suited to automotive and aircraft engine compartments. The new bismaleimide resin pre-impregnated prepreg reportedly does not reach glass-transition below 320°C/608°F. It also maintains oxidation resistance without heat cracks under continuous use in the range of upper 200°C/392°F degrees. Conventional bismaleimide resin-impregnated prepreg has been used in high-temperature applications such as automotive and motorbike engine compartments, but it degrades due to resin oxidation after continuous use at high temperatures and forms microcracks after repeated heat expansion and contraction."