Hey, Brent.
Modifying the ROPS and modifying a FEL bucket are two completely different animals.
1) The bucket is a user option and its purpose is to increase work productivity.
2) The ROPS is a safety device mandated by OSHA for certain applications and certified by OSHA, ANSI, and ASAE (I think....). The OSHA mandate makes it illegal (even to the point of criminal negligence) to use a tractor without a ROPS or with a modified ROPS in some applications. For example, mining and construction.
3) If a ROPS is modified and used in a consumer application, there would be a warranty issue if the ROPS was damaged during normal use, or even a rollover. The warranty would apply only to replacement of the ROPS. No laws violated here. However, as we have discussed ad nauseum in the other thread, the tractor manufacturer is not going to be able to live uip to their saftey obligation and anybody hurt cannot blame the tractor maker.
4) If a bucket were modified and failed, the manufacturer would probably avoid repairing or replacing the bucket--just like the ROPS. In addition, if there were some other damage to the tractor as a result of the bucket modification, the manufacturer might also avoid repairing or replacing a part. No laws violated here, either, even in the example of mining or construction I pointed out above.
The big difference between the consequences of modifying one or the other is less of a a "Warranty" issue and more of a "Product Liability," "Negligence," or "Code Violation" issue. Depending, of course, on whether it was a commercial or private application.
A good analogy might be comparing the the warranty of a hardhat and a wrench. Modify either one and the company might not replace it if it breaks. Modify the hardhat, and the manufacturer cannot promise your safety any more. If you modify a hardhat and put it on one of your employees, look out /forums/images/graemlins/shocked.gif