I like using units that are already used to describe what is meant, e.g. if you have a periodic frequency Hz is totally fine and easy to math with. Now I wasn't aware of Bq, but it makes sense to have a separate unit for the stochastic equivalent.

The only problem with that unit is that it may require explaination. Hertz is a little bit more commonly understood, while someone seeing 2.5 Bq will very likely wonder what that means.

In the end both Hz and Bq resolve to s⁻¹ or 1/s So maybe request/s is just okay as a unit? In the end it depends also on the surrounding UI.