A simpler to disassemble, maintain, repair, and/or upgrade 2-8-0 would be good thing. I converted one to TMCC, sound, and synched puff & chuff, and wished it had been easier to do -- 12 years ago.
In fact, its the only TMCC/Legacy engine that I kept out of the many conversions and factory such engines once in my collection. I just didn't have the heart to sell it knowing that I won't ever attempt that again. Besides it remains a lot of fun to run and Don T did such a good job on them. Terrific attention to detail. Closest thing in my opinion in S to truly a model engine that runs - and beautifully at that.