You assume there are different variables for the main and chain, which is something we do not know given they were never different from one another. Your idea might require more work than you realize If the chain beams are coded with the same variable, then “little chain” would demand completely new coding be done into Valkyrie to separate those numbers.
On the other hand, single beam already exists. It’s there. We know it. It’s how Mercy works most of the time. There’s no need for new animation, the visual is the same, zero new animations needed.
Look, I like little chain idea, and it’s cheap enough to be doable regardless, I don’t believe neither of those two ideas to be prohibitively costly to implement. However, whatever nice improvement little chain brings, it’s still a paliative, a band aid. Little chain still covers for skill, that being target selection, it does so less than current chain, but strong single beam would address that aspect completely rather than partially and thus my preferred idea.