Kalbintion

You have forge multipart in the /mods/1.6.4 folder and the /mods/ - remove the /mods/ one You have two copies of Gregs Lighting - remove the "Gregs lights.jar" "A MOD.jar" isn't being loaded due to improperly formatted information Your jars are badly named and may indicate they are not from the mod authors page - they should be the name given to you by the author so they can easily be kept track of and compared, and if you got the mods from a third party site, they may not be the original mod file and could have been altered to be malicious. I highly recommend to always get the mods from the mod authors pages directly.

Without the launcher log (or crash log if one exists) not much can be done about that other instance of it failing. Also, a modpack api url is preferred but may not be necessary depending on the logs.
 
Getting Crash Logs
* Run Technic Launcher
* Select modpack
* Click on the Cog icon located on the bottom left of the modpack logo
* Click on "Open Folder"
* Open "crash-reports" folder
* Provide relevant log files

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Getting Launcher Logs
* Run Technic Launcher
* Click on the Cog icon located on the top right of the launcher
* Click on the "Logs" button
* Provide relevant log files

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Pasting Logs
Use one of the following methods to show us your log files:
* Attach file to posting
* Use http://pastebin.com and paste the resulting URL in your post
* Use http://paste.ubuntu.com and paste the resulting URL in your post

For overly sized files, attaching or using the above URLs may not work, you can use one of the following for these types of cases
* http://mediafire.com
* http://dropbox.com

Why not just permit users to use commands to claim? It would prevent the need to have an item that does a specific thing.

Probably would have better chances in the actual Voltz server section of the forums...

The launching mechanics were changed to need a constant signal to prevent accidental firings due to a blip of a redstone signal. Don't exactly want one going off in your own base accidentally, do ya?
 
The CC question I cannot answer.

Alrighty, so there's the problem right there. That serendipity pack is for 1.7.10, the Aether II modpack is for 1.6.4. You cannot run 1.6.4 mods on a 1.7.10 pack and expect it to run, likewise you cannot run 1.7.10 mods on a 1.6.4 pack and expect it to run. Looking at the UMS modpack, it is also for 1.6.4, so UMS and the Aether II modpack should be able to be combined without issues (excluding id conflicts of course. and maybe a dependency issue if it was accidentally not copied over)
 
So, to sum that up bit for combining the modpacks:
Aether II Modpack + Seredipity Unlimited = WILL NOT WORK
Aether II Modpack + UMS = CAN WORK
 
As for what files and stuff that needs to be copied over to UMS modpack, it appears to only be the Aether II jar file. And without the log file you got from when you added Aether II mod to the UMS pack, it is hard to state what went wrong.

I would have spend some additional time to actually come up with a server machine that would be able to handle that load of people. I believe it would be around $400 if there was nothing to go from (no case, monitor, keyboard, mouse, power supply, motherboard, etc...) if you wanted to go this route - but also be aware that there is also the network loads that would be necessary to circumvent, and modpacks just increase the network loads, I wouldn't recommend a server on a <1Mbps upload line unless its for about two-three people total (including yourself). For 10-20 ppl on this modpack I would suggest at least a 5Mbps up line, 10Mbps up being more preferred (and may be a bit overkill, I'd need to do some networking diagnostics on the pack to get a better idea of its requirements per person)
 
This all said and done, while I did say I do not personally like any single hosting company out there because of the reasons I suggested, I did offer one option who I have had experience with that wasn't that bad (tho they suffered from the lack of info portion and their customer service leaves something to be desired but their actual server service isnt bad)

You can use the worldborder trim command, it deletes them. Use /wb set <radiusX> [radiusZ] (or another /wb set command) to set the worlds border before running the trim command. The radius needs to be sufficiently set to be outside the farthest from where the command the ran (ie: a base at 100,100, ran at 0,0, needs radius of 100 at least to make sure part of it gets in, 150 would probably get most of their base...etc)
 
Otherwise - use a map editor like MCEdit to delete chunks (bit easier to grab chunks around bases, etc). There is no way though to bypass the chunk edges that will happen from doing either of these changes.

Core mods do not exist in 1.7.10, those mods belong in the mods folder  
Edit: Damn you typo!

That error that you posted btw is a corruption of some information it needs to get. Resetting the pack should typically fix it like you experienced here.

I'd bet the hexxit versions do not match.

I do suggest updating the 1.7.2 mods to 1.7.10 if this is meant to be a 1.7.10 pack, not all of the mods that work for 1.7.2 will work for 1.7.10 due to changes the games gone through and subsequently FML/Cauldron.
 
The issue in the log itself though is in relation to snooper settings not being found then the following line is an error about a file not being found,.
[14:14:31 WARN]: Can't read server snooper settings, won't send any data java.io.FileNotFoundException: server.properties (The system cannot find the file specified) It doesn't mention what the file name is at all, but it does say it saved a full crash log to
C:UsersOwnerDesktopMinecraftServer.crash-reportscrash-2014-08-31_14.14.31-server.txt Which would be helpful in seeing the full stack trace and other info.