The key is determining where the merit sources have to be placed. The who comes later but the mandatory first task is to determine where (section/subsection) and why (numerical justification based on Nº sMerits awarded; Nº posts lacking merits (aprox. human scan in section/subsection)), all in a given timeframe (i.e montly).

Mods as you suggest, or heavy posters/awarders in specific sections/subsections have the topic knowledge that enables them to be better judges when it comes to sMerit awarding).