Any chance we could add nodes to message['params']?

Problem/Motivation

I'd like to be able to modify messages in hook_mail_alter using node titles, summaries, fields, etc but they arent available. user object helpfully is

Steps to reproduce

try to modify message with node data in hook_mail_alter - it does not seem to be there

Proposed resolution

add nodes to message['params'] along with userobj already there

Remaining tasks

use patch or alternative

User interface changes

none

API changes

add nodes to params

Data model changes

nodes are added