The benefits of JPEG kind of go away if you start adopting more recent changes to the format, no? JPEG is nice because everything has supported it for 20+ years. JPEG-with-arithmetic-coding is essentially a new, incompatible format, why not use JXL or AVIF instead?
Yes, but this is really a pity in the specific case of Arithmetic Coding, because, unlike "more recent changes to the format", it's been in the standard since the very beginning - but is not supported by a lot of implementations due to software patents (which meanwhile expired, but their damage remains).
arithmetic encoding is old, but around 2010 (when all the patents expired), there was a ton of really good research on how to to table based ans and vectorized rans to make the performance good. Aside from the patent issues Arithmetic encoding wasn't pursued much because the CPU cost was too high. Now that multiply is cheap and the divisions can be avoided, ANS is a lot better than it used to be.
