@Alikiwi>"Hm, thats a very interesting idea. But then if theres 15 races (which is expected), then you'd need 15 weapons! That's actually doable but I have my doubts I'd get permission, but I'll try"
I think if you are going to make 15 races and still try to make things efficient and practical... then you should consider grouping the races into subtypes. They can still all have their own distinct history and advantages/disadvantages, but you could have 5 different subtypes, so as to make bioweapons and stealing technology possible amongst their own group.
For example (and im just brainstorming here) you could have these 5 subgroups
Category
1) mammalian/avian/humanoid warmblooded lifeform
2) amphibian/reptilian coldblooded lifeform
3) aquatic/squid/fish race lifeform
4) Insectoid lifeform
5) silicon-based/crystalline/rock based lifeform
Planet preference
Race Type 1)Earth like terrestrial planets, high nitrogen/oxygen worlds
Race Type 2)Early Earth type terrestrial planets give population advantages but can also live on Earth like worlds, artic worlds give population disadvantage whereas Race 1 species can still remain productive with minimal tech intervention on icy terrestrial planets.
Race Type 3)Preferrability for predominately water abundant planets, Anything less than 30% water hinders productivity. Can still build on such worlds but with lessened productive advantages and requiring tech upgrades eg water domed cities.
Race Type 4)Can live on Earth type worlds, preferrablilty to early earths and hot humid planets, minimal disadvantages on hostile barren terrestrial worlds. Minimal disadvantages on acidic, methane based planets. Can survive on volcanic worlds with only moderate tech upgrades.
Race Type 5)Suitablity to hot terrestrial planets with geological upheaval. Native to volcanic worlds or sulphur rich venusian planets. Some adaptive tech required for inhabiting terrestrial worlds or highly water based planets. Can survive on acidic, methane planets with minimal tech.
Tech tree discoveries can be stolen amongst same race types. Stealing from other subgroups not native to your own may result a partial gain. This being a slight boost in your own tech research that most relates to the incompatible tech stolen. For example stealing water based habitats from an aquatic race will result in lifting your own research to dome habitats by 25% depending on how far away you are in compatibility to that race. By the same token, stealing dome habitats tech from a reptialian race when you yourself are mammalian may prompt a more favourable outcome like 50% on your own scientific reseach.
This way ensuring the game realism and appeal than having generic settings for everybody
I mean why make 15 races right? if they all have similar advantages and disadvantages to colonising or science and technology.