Size-based link flow control

Our engineering team has the strong desire to add a flow control mode where link-credit is counted in bytes rather than in number of messages.
We’re occasionally getting into the situation where we’re being hammered with a ton of large messages all at once and team is convinced that a byte-oriented credit counter could allow for tighter control of what the client are allowed to push.
For session-based flow control, the permitted windows we need are also too big.
The Flow control section 2.6.7.
in the core spec is surprisingly vague and doesn’t have a hard reference to link-credit being a message counter.
The only hard reference seems to be is in 2.7.4.
where the link-credit section says that “ The current maximum number of messages that can be handled at the receiver endpoint of the link” So we’re thinking about an extra spec with a layered-on capability that allows for reinterpretation of link-credit and delivery-count as counts of bytes.
Thoughts?