Related question, is it at all feasible to store cache locally to offload memory costs and then send it over the wire when needed?

No, the cache is a few GB large for most usual context sizes. It depends on model architecture, but if you take Gemma 4 31B at 256K context length, it takes 11.6GB of cache

note: I picked the values from a blog and they may be innacurate, but in pretty much all model the KV cache is very large, it's probably even larger in Claude.

Yesterday I was playing around with Gemma4 26B A4B with a 3 bit quant and sizing it for my 16GB 9070XT:

  Total VRAM: 16GB
  Model: ~12GB
  128k context size: ~3.9GB
At least I'm pretty sure I landed on 128k... might have been 64k. Regardless, you can see the massive weight (ha) of the meager context size (at least compared to frontier models).