"The contribution of concentric strings to the strength of the structural casing is small and difficult to quantify due to the unpredictability of the cement linking the internal strings to the structural casing.
Assuming that the annuli will be cemented doesn´t improve the structural strength of the system. Appendix H outlines the results of tensile test of cement. Cements have a very low tensile strength and low Young´s Modulus relative to steel. The contribution of "uncracked" cement is minimal due to the low Young´s Modulus relative to steel. The cement will crack during high bending loads reducing EI (Young´s Modulus and moment of Inertia) of the cement."
Good cement, well centralised pipe, a good slurry pumped at a good rate will help to assure well integrity. Getting it to surface is not essential. Getting above the maximum bending load point of fixivity perhaps is?
The key hazard/risk is surely a problem zone identified or known just below the conductor that cannot support the weight of the cement column. And why even conventionally we would pump a light lead wait until we see returns at surface then pump a heavy tail at the end. If no returns then you are into running a top up string. An extra trip where at about $1 - $2m trip time costs the light weight cement seems a cheap and more assured option for many.
We have been using 20" TAM ECP system in 30" countless time now.
They have been pretty reliable with one or two failures mainly because of the human error. One I can remember was incorrect pumping procedure to inflate the packer.
But these are mainly on platforms and shallow waters ~150m. So manipulating port collars with combo tools may be easier in our case.
With your cementing flow rate inside 36" conductor this ECP will hardly add any additional ECD. We don't notice in 30".