There was a Battletech MUD??? That's so cool :) MechWarrior 2 is what got me into it as a kid
The granddaddy was 3025, followed. T 3056 - these were attenpting to portray the entire BT universe. So you’d sign up, join a faction, be assigned to a unit, train with your peers, and eventually go off to fight (though I don’t think either ever reached that point).
World level scenario based spinoffs started to appear. Planet level battles between multiple factions. Same deal as above except you would leave base with your unit to a shared hex map and could encounter other opponents.
All in all a much truer experience to TT than the MW games, but less so than Megamek
I multi-factioned for a while (shame shame!) and had a low level character in the DC. The way you all did mechwarrior training was so much more hardcore than all the other IS factions (never played as clan). It was also the one major faction where I never even came close to getting a character into their SpecOps unit(s), not sure if you all realized how much better you were than everyone else skill-wise lol.
Eventually I wound up in charge of Marik and that ended all the time I had for multi-factioning.