Why would anyone want to play Poland on civ 4?
As for portugal. Found this below.
http://en.wikipedia.org/wiki/Portuguese_colonization_of_the_Americas
I always thought the game centred on the northern Americas including America and canada? perhaps this is why Portugal is not included?
Perhaps Portugal or other nations could be added as a 5/6th civ on an
expansion pack. Bit like civ 4. you have 21 but you only play with x civs in each game. I think the way they have done the civ bonuses like immigration it might be hard to add more to this. If more than 4 civs played you may need a larger map. Would be fun to see an indian tribe with 10-20+ settlements.
Give them all the arms and horses they need then make them declare war on your enemies. hehe.