Great question! As a small manufacturer looking to automate on a budget, you're thinking smart. The good news is that you can absolutely get most of the benefits of a full S7-1500 system without breaking the bank.

For your minimum viable setup, I'd recommend starting with a Siemens S7-1200 PLC. This is the perfect entry point - it's about 30-50% cheaper than the S7-1500 but still gives you around 80% of the functionality. The S7-1200 is designed exactly for small to medium-scale automation like what you're probably dealing with. It handles basic to mid-level tasks like packaging machines, conveyor systems, and small process control beautifully.

Here's what you get with the S7-1200 that matches the S7-1500 experience:

• Same TIA Portal programming environment (so your team can use familiar software)

• Good communication capabilities (PROFINET, Ethernet)

• Solid reliability and Siemens quality

• Expandable with I/O modules as you grow

• Works with many of the same HMI panels

Now about mixing components - yes, you can mix within the same generation family pretty effectively. The S7-1200 and S7-1500 both use TIA Portal, so you can program them similarly. However, there are some limitations:

• You can't directly swap CPU modules between the two series

• Some advanced S7-1500 features (like certain motion control functions) won't work on S7-1200

• I/O modules are generally not interchangeable between series

My advice: Start with an S7-1200 system, and if you need to upgrade later, you can migrate to S7-1500 while keeping much of your programming knowledge and some peripheral equipment. This gives you a solid foundation without overspending upfront.