So yes, I have attempted a modification of the default player list.
Said mod adds two extra fields to the player list.
It also let's the server, weather it be by other mods or the host, manually, choose what values they should represent.
The mod is here:
http://www.gamefront.com/files/20139443/System_Syerjchep.zipAnd it looks like this ingame:

By default the two buttons will just say "N/A1" and "N/A2" but it relies on a mod to change that.
Here's a modified version of Kalphiter's infinite mining gamemode that makes those values track money and dirt mined:
http://www.gamefront.com/files/20139446/Gamemode_Mining.zipThe way this works is by adding code into the script like this:
if(!$syj::loadedvarprefs)
exec("add-ons/system_syerjchep/server.cs");
$syj::loadedvarprefs = 1;
$syj::varprefoverride = 1;
$syj::primarytitle = "Money";
$syj::secondarytitle = "Dirt";
$syj::primaryvar = "mineMoney";
$syj::secondaryvar = "dig_dirt";
That is at the start of the gamemode script.
The first two lines check to see if the mod has been executed yet, if not, execute it.
The rest tell the mod that the prefs don't need to be reset and what values to use.
The "title"s are the names of the buttons that clients will see on their new player lists.
And the "var"s are the actual vars. Taken as a child of the client. If one of my vars was "money" the mod would update with '%client.money' each time.
Then, at the position in the script where the player's money and dirt count are updated, there is this script:
updatefirstsr(%obj.client.bl_id);
updatesecondsr(%obj.client.bl_id);
Which tell the mod when to update the values, rather than just using a loop for every update.
The mod also takes trust values, button clickability, and side button functions from the old list.
The mod will not add an index to the new player list that has a BL_ID that was not on the old list, to prevent abuse.
The mod disables itself in servers that do not have the mod themselves, and enables it on servers that do.
I have posted this in Mod. Discussion because I feel I still need more testing before I post it in add-ons.
If you find any bugs or problems just tell me and I will fix them, though I have tried to test this myself, it was often in
single player, which makes less applicable results.