The Secrets of the Iron Titan

From publisher blurb:

Become More Machine

This new 1st -20th level base class is designed for use by player characters at every level of play; allowing the character to emulate an iron golem, a transforming construct, or a watchman brought back from the dead as a cyborg.

The iron titan gains a pool of points it can use to select specific construction builds similar to how a summoner's eidolon works. The iron titan becomes more and more mechanical as it advances untill ultimatly it becomes nigh-indestructible. This class can also be easily introduced into any new campaign assisted by a simple plug and play style first person introduction.