Question regarding proto modifications between chained services

[Asaf Ben Aharon]

Hello, 

I have a chain of 3 services (A => B => C) and a simple proto message (M).

A and C hold the latest version of M while B holds an old version one (let's say that B has no field 'foo' in M's schema while A and B have it).

B receives an instance of M, enriches it, and passes it to C.

Is there a way to preserve the values of 'foo' while B modifies this message, so C will have both 'foo' value and the enrichments?

Thanks!