@SageLichtenwalner - As someone with extensive experience with the pre-2015 program, you are on the money in concluding the current program is far more simple. In the all-paper era, it was a huge task to figure out whether each boy advanced and how many arrow points he had earned.
Going back to 1942, when the Wolf, Bear and Lion ranks were decoupled from one another (prior to that, the advancement system was a progression of the three ranks), the idea was and remains for a Scout to have a set of requirements to meet over the course of a year and be recognized for it. Whether the rank was earned or not, the Scout moves on to a new challenge the following year. It isn’t that astronomy is a bad topic for Wolves but a good one for Tigers (Sky is the Limit adventure), it’s just that astronomy is compartmentalized into the Tiger year, so there is room for other topics in other years, Astronomy returns for Webelos Scouts, This keeps the program fresh as the Scout moves through the ranks.
The new program addresses immediate recognition with the adventure loops. For most of teh exitence of the previous format, Scouts were not recognized at all until they completed their rank. Now they get bling along the way. For the final 35 years or so of the old program, there was a Progress toward Ranks device worn hanging from the right pocket. Scouts received a bead after completing three achievements. There were yellow beads for Wolf achievements and red beads for Bear achievements. Try to imagine what it was like to keep track of which Scouts had been presented which beads with all your records on paper. You also needed to keep an inventory of the beads. Since not every Scout finished, you had beads left over at the end (which was good, because they would fal off the thong, and Scouts would lose them). Many packs opted not to use them at all.
Adventure loops are a serious upgrade to the effort to provide immediate recognition.
While at first glance, it might make sense to provide more opportunities for Scouts of all ages to compete requirements together, if there are Tiger, Wolf and Bear astronomy electives, when will the Wolves have time for archaeology (Digging in the Past) or Bears have time for Robotics?
All ranks have hiking, outdoor activity and service project requirements. My pack tries to get these done all at once as pack activities. But once yet get away from things of a general nature, the program stays fresh if the Scouts work on such things as a den.
Aside from being a Cubmaster, I’m also a GSUSA troop volunteer. So, Lion/Tiger = Daisy. Wolf/Bear = Brownie. Fourth and fifth graders are Juniors. In some ways, the two-year program is advantaggous, because you can engage in things that take longer to complete. Girl Scvouts work on Journeys, which are modules comprising several badges each. A Journey could take a few months to complete, and it’s a deep dive into a subject area. For example, the Brownies in my troop recently completed the Wonders of Water Journey, which they started in the spring but didn’t work on over the summer. They learned about conserving water, scarcity of water, pollution, and sharing water. They also completed a Take Action project composed of a publicity campaign in which they advocated for water conservation. There is nothing Wolves and Bears do that is so comprehensive as that. it would eat up almost half of either the Wolf or Bear year if there were such a thing.
Diving into your point, we should ask: What of Scouts could work on the Wolf and Bear ranks simultaneously during second and third grades? That would help smaller packs that need to combine dens. It’s hard to see what the disadvantage would be. The one thing that comes to mind is Whittling Chip. If we continue to not want second graders handling knoves at all, that activity would need to be restricted.
I think combining Lion/Tiger into a single two-year program would be more difficult. Many Lions are simply not ready for some of the Tiger adventures.