Hi, it may just be a file naming problem. For a texture pack to work within a resource pack it needs the correct folder names etc. If you get the raw 1.5.2 version of the pack and throw it through Dinnerbones Texture Ender it converts it to a 1.6.2 compatible version (as a rough fix).
Yes possibly however that would take quite a bit of processing power, perhaps maybe a separate PI to use as the server which others may connect to? I'm not sure, coding isn't particularly my forte As of yet there are few mods for the PI Edition however it should certainly be possible to make some
The Raspberry PI is a small credit card sized computer which can be bought for about £25(UK) and is also available nationally!
Essentially it is a very small PC and to allow Minecraft to run on it a cut down version of the game was required so Mojang produced Minecraft PI Edition! Its similar to Pocket Edition for Android and iOS.
I myself own Rapberry PI and I would say get one (but I can't because of Rule 6)! They do take some know how to get working though! Hope I could help, Frog2face