Short version: Possible yes, likely no

Long version:
Pokemon generally has a lot more love and fanship behind it especially when it comes to English users. With a smaller fan base means that less users are developing things for Digimon and ultimately there are less tools available. However as you mentioned there is Ds game maker or devkitpro that assist in making homebrew. For this you would therefore have to know a fairly large amount of coding though, designing menu screens, party screens, saving, loading, battles, battle mechanics and basic animations.All of this is highly possible but due to your self said that are new to programming it would take a decent amount of effort to get to a point in programming that would be able to achieve a Digimon game. So yes you could make a homebrew of it but is probably going to take a lot of time, effort and learning.

If you aren't so set on working on homebrew on the ds and instead just working on a digimon project you might be interested in pokemon edits that have included digimon instead of pokemon. For example Digimon Firered but a google search will find you a bunch more.

Regardless, good luck to you.