Hi Giovanni,
Firstly please apologies for my poor english.
If you are familiar with Labview, then the LOGO is for you ! The programming interface is simple to install (and free !) and you could create a PI loop in seconds, and other amazing functionnalities. I think that the LOGO largely fullfill your requirement. From my POV other PLC are costly and harder to do the same. The practical limitation is on the side of I/O and communication. Effectively 'spaghetti code' could be a bit annoying but you're familiar with that, isn'it ? Be aware to keep the source of your code.