The Highlander is definitely a classic Capellan Mech, based on the redone availability. They had the Northwind Highlanders as part of their army for ages. They had both Hollis Industries and Star Corps plants capable of building them for several years, decades, or even centuries before they went back and forth between them, Marik and Davion. The Highlander can be seen as an inspiration for the Vindicator.
They're both tough, generalist low speed troopers that uses jump jets for better mobility. They can be the linchpin of a lance and work great in groups. Plus, the Capellans need a break during the later Succession Wars. The Highlander is a nice gift for that time.