We already have this availability for servers to a point (Not in a software package but its just the nature of our server packs), you simply go to the server download page right click on the server you want and copy link address. Then (Assuming unix distribution) use wget or simular to download it into your server dir: "wget http://www.creeperrepo.net/direct/FTB2/currentMD5/modpacks^Ultimate^1_1_2^Ultimate_Server.zip" Then generally I like to move it to a more meaningful name: "mv modpacks%* ultimate_update.zip" Then finally unzip using your favorite unzip package: "unzip ultimate_update.zip" overwriting all the files.
This assumes you have not made any config changes if you have then you will need to go and manually change those again because our configs generally change between versions so to avoid miss matches you should always start from scratch in terms of configs and just keep a note of the configs you want to change.
I understand that it might not seem the most streamlined process for some but I guess if you are running your own server then you should be able to manage this without issue. If you are using a minecraft server host they will probably provide updates for you so you dont need to worry about it which is generally the best solution for people to simply play the game rather than run a gaming server.
If there is enough demand for this then I might do it but I honestly don't see the demand for it