Upgrading Smokes to Smoke/CO (System Sensor) - confused?

Hi, 
 
I'm trying to add combination Smoke/CO (COSMO-4W or COSMO-2W) to my current system of 4-wire smoke detectors (4WT-B), but I still have a number of questions after reading the docs from System Sensor. 
 
Current System:
 - 4WT-B smoke/thermal detectors
 - 3 independent 4-wire loops (basement, 1st floor, 2nd floor).  
 - mechanical thermal detector in the kitchen (connected to the 1st floor 4-wire loop)
 
Upgrade Questions:
 - My first though was to use a COSMO-4W detectors along w/ the COSMOD-4W module (given the current 4W wiring). However, since I have 3-independent loops, this means 3 COSMOD-4W modules, correct?
 - However, based on the documentation, I believe that I'm unable to re-use any of my 4WT-B detectors w/ the COSMOD-4W sensor. All would have to be upgraded to the 4WTA-B or 2WTA-B, correct?
 - It seems like that 2W system offers more features by monitoring additional trouble and maintenance conditions on the trouble zone that aren't possible to monitor w/ the 4W system. If so, what are the advantages w/ staying w/ the 4W-based system? I think I can also wire everything in one zone w/ the 2W system as I can use the other two conductors as a return path. 
- If I go switch to the 2W system, am I unable to wire the mechanical thermal detector in the kitchen; as the 2W loops cannot have mechanical thermal detectors on them. How do I wire that detector then? 
- If I go w/ the 2W system, should I use the other conductors to create a "LOOP STYLE D / CLASS A WIRING"? What would be the advantage of having that? 
 
Thanks for the advice. 

So I'm thinking of the following strategy; any issues:
  - put the 2nd floor and basement on a single 2-wire loop w/ a COSMO-2W unit (I have 4-wires running everywhere, so I can daisy chain all the detectors and have a loop going back to the panel). 
    - wire to 3 zones in the panel - smoke, CO, maintenance
    - wire smoke/co triggers b/w the two loops 
 
  - put the 1st floor on a 4-wire circuit w/ a COSMO-4W unit (this will have a single SMOKE/CO combination detector and a mechanical heat detector in the kitchen). 
    - wire to 2 zones in the panel - smoke, CO; 4W unit doesn't support a maintenance zone
    - wire smoke/co triggers b/w the two loops
 
Can anyone poke holes in this strategy? Am i over complicating things?