This may not be an answer you're looking for, but you can do this with the Curse Voice launcher... after you have a profile loaded, when an update is released the icon will show a little symbol at the top that looks like an underscore with a downward arrow on top of it. If you put your mouse on the icon without clicking, the Orange "Play" button will appear and underneath that will be an "Update Pack" selection.
Click the "Update" selection and the pack will update without starting to play. I do this because I like to add both "Iguanas Tinkers Tweaks" and "Veinminer" to both Direwolf20 and Infinity before I start playing.
I think if a pack is recommended it will ask if you want to update when you click the Play button without giving you a chance to add other mods.
I like to run beta packs so I have my profile settings changed from Recommended to Beta... In that case you have to manually perform the update as indicated above. You will have to re-add your additional mods, but at least it keeps the previous keybindings