Certainly no limos....
I understand what you mean, however remember that the cult attempt to appear not to want to take on any attention until it is too late. So standard 'trucks' should also be the go to offer transportable firepower and masses of troops. Lightly armoured and cheap (much like the orks have).
It depends how far along you want it. Even in the event of civil war and the split of loyalists vs cult, Chimeras would not really be the majority purely for the sake of where the revolt takes place - within cities and hives, not on the battlefields.
Much like the civil war in Libya at present and African warlord states, there are armoured carriers, however necessity and cost sees the use of standard transports as a viable option.
Limos? Well that depends on the ego of the Patriarch does it not?
Other question: Is the list intended for a 3000 points force or is it a minor list only made to see small forces of say 1500 points? The issue is that (from my understanding) there really is not much literature on planet wide cult revolutions? How far back do you intend to go for a gene-cult list as well? The initial idea was that they consisted of chaos cult forces as well as they were easy to infiltrate.