Target structure

After completion of a few first steps wit RPi and launching 1-wire temperature sensors (DS18B20), a potential target list of RPi functions emerged:

Meaning:

Communication with 1-Wire DS18B20 sensors, which will be placed in all the rooms (I have many wires free and available; all wall-mounted switches are connected with CAT5 cables). A multi-point measurement will allow for a better assessment of the real/felt temperature. The existing single-point temp. sensing is imperfect,
Measurement of air humidity for the needs of controlling a recuperator. It is still in plans, but when it is installed I should be able to modify its work according to readings of humidity.
Measurement of soil humidity needed to correct the garden-watering programs,
Light intensity measurement, which should help to optimize the programs of window blinds and automated lights on/off settings.
Communication with my Viessmann Vitodens 200 on the basis of solutions offered by openv. I do not, obviously, need to override the built-in weather automation. I do however want to change the programs/temperatures and water pomp setting from a single PLC visualization depending on the needs of the householders, guest visits or the temperature of my fire-side. RPi has a RS232 port, which can be used. That should let me avoid buying another RS232 module for my PLC.
Sending email with pictures from the IP cams or storing pictures according to signals sent by the PLC. The PLC itself, although it sends emails and data to SQL databases, cannot attach/store images,
From outside the PLC-realm: function as a file server or a torrent client.