On second thought, I don't know what the exact FOV and zoom factors for the different ironsights and scopes on a default config are, so that number is most likely wrong.
I'm using cl_ads_fov_scale 0, so ironsights don't zoom in at all, therefore ironsight sensitivity scale is at 1.00 because ironsight ADS and hipfire FOVs are identical.
Scope sensitivity scale I also have at 1.00, but I'm using cl_zoom_sensitivity_fov_scope 0, which uses world FOV for sens scaling when scoped (same as RO2/RS/RS2) because I feel that the default behavior (sens scaling using FOV inside scope) is much too slow at the higher zooms.
Anyway that's what works for me, instead of overthinking the myriad sensitivities in this game that is a bit of a clusterfuck.