The common thing that these changes aim to do is to improve green's aggressivity:

• Yavimaya Elder is venerable but Jadelight Ranger can be a decent beater sometimes while the former is just destined to die.
  • 4->6 mechanical themes contributions.
• Undergrowth Champion has a built-in protection but it doesn't come around that often and undermine it's potency each time. Tireless Tracker add card advantage to Landtraffic and Counter contributions and may support a artifact token subtheme in the future.
  • 3->5 mechanical themes contributions.
• Forgotten Ancient is bad signposting as it may imply that green could be a good spellslinger or storm color in this cube. Meanwhile, Esika's Chariot can copy token wich is a good reward for selecting big token makers. It also help a little the Tap/Untap mechanical theme.
  • 1->4 mechanical themes contributions.
• Mouth//Feed is simply too average: Ranger Class produce immediately a 2/2 for 2 instead of a 3/3 for 3 (wich is faster if not plainly better) and after that it could generate a lot more value in a long game.
  • 4->4 mechanical themes contributions.