[quote=@Duthguy]
I'm not familiar with Digimon frontier, they only dubbed and aired adventure 1 and 2 here but I'm throwing in my interest
[/quote]

In terms of digivolving, frontier was the inevitable destination for a logical progression taking place; in 1, the kids help them digivolve, in two,  they briefly bring back an unnatural digivolving process with the armor and also help the digimon evolve by fusing two. In three,  the kids themselves would fuse with their digimon to get them to mega level,  and finally,  frontier; kids find "spirits" initially represented by small idols, not unlike the eggs necessary to armor digivolving.  Using the spirits,  the kids would employ "spirit evolution", skipping the digimon partner angle and having the kids just turn into digimon themselves from day one.