at the moment I am collection (dis)advanteages for a 2 tier or 3 tier architecture.
Maybe you have some additional points
Quality tests can only be done with high effort
System has to be connected to several systems (at least development and quality ECC)
Fits to ECC Architecture where you have normally a 3tier architecture
Development can be done in parallel to tests
Mass tests can be done easier
Possibility to use Q as backup system in case of Problems with Productive system
Additional effort to keep system in synch (service package etc.)
Or would you already go to a 4 resp. 5 tier architecture?
Thanks for any input