So if you want to play Crackpack (or any other modpacks in the Curse/FTB launcher) without having to open the annoying Curse app, here's what you do. First, you do need to install Curse and download the modpack you want. Run it once (just open the launcher; you don't actually have to hit play from the Minecraft launcher). Once it's installed, go to the Settings button in the Curse app, click "Minecraft", and then copy the address listed as "Minecraft Install Location".
Next, open Notepad/TextEdit (or your text editor of choice). If you're on Windows, copy-paste the "crackpack.bat" file below into your text editor. If you're on Mac or Linux, copy-paste the "crackpack.sh" file below into your text editor (warning: haven't actually tested this one). On the first line, replace "REPLACEME" with the address you copied from the Curse app. Then save it as "crackpack.bat" or "crackpack.sh". On Mac/Linux you might have to open a terminal and run chmod 700 crackpack.sh; too lazy to test if this actually required.
Anyway, now you should be able to just double click the file to run the launcher. You can entirely close down Curse now; it's unneeded. If you're on Windows and you don't like the fact that you get a command line window when you run this file, follow this guide to get rid of it.
Oh yeah, this might break if you happen to have a different version of Java (I think they've locked it down to 1.8.0_25 but I guess they'll probably update someday). Uhhh, if that happens, go to the folder you filled in as the REPLACEME earlier, and then go to runtime/jre-x64, and see what the version number of the folder inside there is, and then update line 3 of your crackpack.bat or crackpack.sh file to use that version number.