Things are not always as simple as they may first appear.
Not having seen the asm yet i think it's a bit presumptuous to assume you can make sparkling changes to a program that has been worked on and refined over a long period.
Having said that, you can find the start of the 12F683 discussions here. It's all open to changes for the better so good luck.
http://www.rcuniverse.com/forum/m_10662258/tm.htm