we are a small company and name surrogates while absent. When naming substitutes this is accompanied with a written handover in our wiki. The extend of the handover between the role holder and the substitute is defined by the extend of the absence period.
From our perspective this applies best to 2.5.4 (a) of the constitution.
A possible voting upfront (which i have seen in other - traditional - companies) would (a) not be aligned with the constitution and (b) create some more administrative overhead in at least duplication voting efforts - which will slow down the development of a company.