Alignment in CF does not have any kind of sliding scale as it sounds like you would like for your character where over time he shifts one way or the other as needed, while it is worth noting that just about anything in cf is possible as long as it is RP'd well enough, I would not recommend trying something like this. Alignement changes always come at a high price in terms of lost abilities even when the change is well thought out and rp'd well it can require the greater part of a characters life to make the change and even longer to recieve those lost abilities back.

The way you describe wanting to play your character sounds like you want life events to influence your character greatly, so much so it will change a fundamental part of his being, in cf people are born good/evil/neutral it is an inherent part of their being, to change this based solely on your environment without any clear idea of the how/why of it before hand is more then likely going to cause frustration on your part.

What I would do if you really don't want to pick an alignment is go neutral and refrain from becoming overly concnerned in any one struggle, i.e. don't become a crusader for the light, or become a mass murderer, etc, just go with the flow of events around you. This way you can intereact with all characters pretty much how you see fit and maybe after you've played a couple characters (I'm assuming your pretty new, sorry if your not) you can try something as challenging as an alignment shift. The main thing to remeber that the characters who have gone though alignment changes most successfully have generally had excellent RP 100% of the time, if your wishy washy about it don't except anything but a hard time.

Hope this helps, sorry for the length, work is slow today