The usual reason for using modpacks is modded servers. However, the description requirements for curseforge modpacks are sufficiently great that many server owners, especially of small servers, don't have the time to upload modpacks to curseforge, especially with the length of time for project moderation.

I entirely understand the requirements for detailed descriptions and manual moderation as an attempt to avoid malware and spam for packs that are publically available. However, since server modpacks don't need to be public, then the obvious answer is to use manual import.

However, that comes with another issue - when manually importing a modpack, it always creates a new instance, which means all of a player's custom settings are reset to default. When playing with several mods, often one needs to rebind many keys to avoid conflicts, and I personally use a stream deck to avoid having to remember the keys for the more common modded actions. Having to rebind all my keys after every update is a massive pain.

Therefore I suggest, as per the title, the ability to import a modpack into an existing custom profile. This would apply the same functionality as updating a curseforge modpack does, just using the local modpack file instead of one hosted on curseforge.

From a technical side, this would require curseforge keeping track of what mods were installed whilst importing, so as to know what to remove when updating and what is a "user added" mod and therefore should be left.