although this is self-hostable on gcp, they can get quite expensive due to the machines used. cheapest vm with nested virtualisation on gcp costs about $60/mo. on aws, you'd have to go with bare metal, which can cost you a lot more.
i think the next best thing for sandboxes is, "vm as a library", atleast for personal/small scale workloads.
do you think the "bug" exist in the latent space? i don't think all bugs does.. the bugs exist as long as variant exist in the trained weights. until we have some kinda rl env for verifying bugs.. its never gonna work "well".