i use this in my mod and it works quite well actually. all civilizations in my mod have many units that require population to build, but the 'early' units do NOT require population. the result is that the AI will build new cities and often defend them with these 'early' units, and once the city is established, the AI will build units that actually require population points. this allows the city to 'grow' first before the AI utilizes population points on stronger units. =)