OP, the CPU and memory usage for Tekkit is (for the most part) caused by Buildcraft. Bugs are bugs. Tekkit can't push a new update every time a bugfix comes out, because server owners everywhere would miss the memo and bitch when their clients can't connect because someone wasn't watching their version numbers. They try to grab the most-stable (at the time) version of each mod and cram them together.
The bugfixes will be implemented in due time, of course, but it's not possible for Tekkit to stay up-to-the-minute with new versions. The devs behind the pack have personal and work lives that (believe it or not) don't revolve around Minecraft (also the client-server version mismatch problems from not paying attention).
If you want to add and fix stuff and submit a modpack.jar to the team, then by all means, go ahead! You may very well make someone's job a hell of a lot easier, and expedite the process of the current dev cycle.