Espresso
From personal experience, formerly involved in government procurement processes, I believe the only way to go (espescially for smaller nations) is COTS.
Let the manufacturers present their goods from a fairly broad and simple set of requirements, then decide what best fills your requirements vs cost, and there you have it (Make sure you have a fire proof contract, including OEM logistic support)
Examples of success:
Sweden, 15 Blackhawks off the current production line, including training and support.
Norway, C130J, off the current production line. In service within 18 months of ordering.
Examples of failure:
Norway, New SAR Helicopters. Procurement program initiated in 2007, and still has not produced anything other than papers and unrealistic requirements. Latest in service forecast 2020. Original Seaking replacement was scheduled for 2008.
Norwegian frigates (similar process), supposed to be a state of the art multi-purpose weapon system.
Turned out to be a weaponless, out of date ASW frigate. Mostly due to the time it took from project start until it was finished, but also due to the "We must specify all aspects of the procurement ourself, and under no circumstances buy anything already available" mentality
Torcher