Z-Wave capable OpenTherm GW and thermostat?

[cybericius]

Hi All,

I am new to smart home and therefore Domoticz.

I'd be happy to browse through all the details, but due to the vast amount and lots of different approaches I feel being lost to study all of them. Especially due to the fact that I think I tried to find a solution for my problem, but seems like it doesn't exist.

Nevertheless, I don't think my expectation is extreme, let me explain:

EXISTING CONFIG:
I have an existing setup of a Remeha Avanta Plus 24S boiler and an accompanying Remeha c-mix controller. Both are capable to accept OpenTherm messages.
My Remeha iSense thermostat is on the roof level of the house, but the previous owner didn't plan in-wall cabling for connecting it to the Remeha c-mix controller that is placed downstairs.

PLAN
Maybe my approach is not right, but I plan to connect--if possible with Remeha iSense, if not then with something else--the thermostat wireless to the Remeha c-mix panel, so that I could send the signal of the thermostat in air. The problem is that the Remea c-mix controller only accepts wires.
I assume, a gateway element is needed to be there with wires connected to the Remeha c-mix controller that can accept wireless OpenTherm messages and relay them in between the thermostat and c-mix. Also, I think I need an element connected with wires to the Remeha iSense thermostat that can relay then the wireless OpenTherm messages in between the thermostat and the controller. This is my first priority.

EXTRA PLAN
In my standard approach of a plan, I haven't specified any protocols to be used for propagating the information in between the thermostat and the controller. Maybe it is irrelevant after all. BUT! I would like to have a smart home, most preferably a Z-Wave system after my studies so far.
I vision that I could have a Z-Wave hub/controller that allows me to access and manage my devices remotely and learn/schedule activities, preferably via Domoticz, or other web platform. As heating being part of it, it would be great to see and change temperature of a thermostat set point, or control other thermo valves (e.g. FIBEFGT-001 Fibaro Heat Controller).

ASK
Please tell me if there is something illogical in my plan, and if there is, what that is. If my plans sound reasonable, then what elements/solutions I could adapt to my situation to achieve the goal? I like to prefer open, community favored systems that have wide compatibility. And I am not afraid to build SW/HW system/boards on my own.

Thank you for the help in advance!

[cybericius]

Attached is the topology.