Can People Work on It? If your system needs repair or modification, it's easier to find a developer to support generic languages such as Microsoft Visual Basic or Oracle than specialty programming languages.

2. You need to invest time and people to learn the system and thus can make the modifications. The time and money invested sometimes may be higher than develop from the scratch.

3. The modifications need to be tested extensively to prove it works as expected. The packaged system itself has been tested before it is shipped to you. So a lot of modifications require extra tests.

4. The modifications may not be compatible with the original architecture design, so making the maintenance difficult.