In the narrative of my games the mech commander of my Red Hand mercenary group built the company on an inherited family Mackie.
This venerable battlemech has seen combat, and survived combat for hundreds of years...
...but how does that translate over to the tabletop?
Tactically I find the Mackie works as a constant weapons platform- the AC 10 and the PPC dishing out 10/10 damage a turn at range. I want to hit as much as I can every turn, so movement is about getting into a good position- cover if possible, and just firing away. If opposing mechs close we switch to the AC 10 and two medium lasers, followed by kicking.
Mackie has no hands, but at 100 tons a kick can take most light and even a few medium mech legs off- heavies and assaults also don't like being kicked, but you miss the 1 in 6 head shot, and have to make a potential pilot roll not to fall down, so I tend to kick less vs. punching. The Mackie is certainly "fun" to play like the Urbanmech, but it needs good lance integration given its limits as a 100 ton mech.
Most 100 tonners have a better mix of weapons and more weapons- dual PPC, AC 20 LRM systems, medium laser arrays- look at the Awesome, Battlemaster, and Atlas as examples.
At 100 tons you want to get more weapons on the mech, which the Mackie lacks so that shortfall needs to be made up with other mechs for flexibility.
Do you want a 100 ton pillbox?
When was the last time you saw a Mackie on the table?