Appreciate the post and feedback.
We want to alleviate concerns that SIR & EA3 are the only steps we're taking towards bringing Pioneer to Arena this year. While we don't have anything to announce yet, we can say that we are planning to have more older cards added to Explorer this year and into early next year.
Many cards in EA3 do bring Explorer closer to Pioneer, and that remains the primary goal. But, it is not the only one. Just like Magic sets have different cards for different audiences, so do anthologies and remasters. Development costs also affect which cards are included.
If you are one of the folks interested in this topic, we are planning on speaking to this at our Gen Con panel on Aug 5.