We would have to pick another command for this. M116 is the Wait command.

"Wait for all temperatures and other slowly-changing variables to arrive at their set values if no parameters are specified. See also M109."

But I think what you really want to implement is either an extension to M115 or (for best compatibility with Repetier Firmware) the M360 command.

We prefer not to add features that require a pile of strings for all configurations because Melzi boards have a limited amount of space.

We prefer not to add features that require a pile of strings for all configurations because Melzi boards have a limited amount of space.

The strings can be shorten if they look a lot, like those on Repetier Firmware M360 or even shorter than those or even report as CSV values like:
AREA: 0,200,0,350
XPOS: -10,200
YPOS: 0,200
ZPOS: 0,170
or (CSV)
AREA: 0,200,0,350
XYZPOS: -10,200,0,200,0,170

. Also these will be reported only when EXTENDED_CAPABILITIES_REPORT is enabled. This way it does not look like it can be a problem, or does it?

If hosts are doing an M360 command as standard practice at this time then I guess 🙄 we may as well adopt it, but it should be disabled by default, and I suppose the feature which enables it can be called REPETIER_GCODE_DIALECT.

I'm not very fond of having these as part of M115 mainly because they can change as different tools are selected and as the workspace changes with M53 - M59.

As an alternative, these parameters could (also) be added to the M408 command which is being added as part of PANELDUE support #10610, but which is also going to be enable-able under an option called RRF_GCODE_DIALECT.

I think putting the bed/build area reporting under REPETIER_GCODE_DIALECT is not a good idea as the bed/build area are the most common and basic settings in every 3d printer regardless of the Firmware flavor.
Reporting the X carriage Min and Max for both carriages X1 and X2 to the host seems good for the workspace changes.

Rebased and squashed. To update your working copy use the Git Console and the following commands:

git fetch origin
git checkout bugfix-2.0.x
git reset --hard origin/bugfix-2.0.x