My recent campaign has been run in arcs of 4 to 6 month, between which we usually change system and rebuild the characters due to using a Work-In-Progress custom system. My players and I have been curious about using D&D a few times, but the leveling curve is bugging me. 

My problem is that I do not expect the players to gain more than 3 levels during the course of an arc. Most classes gain a single major feature per level that may not be interesting for the player. Most numerical features increase every 2 or 4 levels. Same for spell-casters unlocking a new spell level. This is especially a problem because in our current system, level-ups give a lot of options and possibly very useful features, closer to the effect of a new archetype or a feat.

For this reason, I would like to let players take 2 character levels instead of 1 during a level-up, so as to make sure that their features upgrade and that they get at least a new one that interests them. If they like all of it, all the better. Over the course of an arc, instead of going from level 3 to level 6 (gaining a feat, a damage upgrade at 5 and a usually non-combat feature before the finale), they would go from level 3 to level 9, unlocking the usually much more impactful features of level 9 and/or 10.

**Are there any unintended negative consequences to this?**

*For the record, we use Milestone leveling for simplicity. The players can expect at most three major level-ups during this time, those usually gave to completely new abilities or huge power spikes. The gameplay itself is usually light in combat, although a D&D game would probably have more.*