I don't know if your hair will grow back softer if you repeating tweeze your head. Repeating tweezing your head should cause damage to your roots which will cause less of your hair to regrow so your hair will almost certainly be thinner.
When my brother was in law school he ended up pulling his hair because of the stress and his wife said that when his hair grew back it was much softer initially.
It's hard for me to tell whether tweezing has made my hair softer. I've lost some hair so it's a little thinner, but not a ton.
What I concluded from my experience was that in order to effectively go bald I would have to maintain a tweezed scalp, Fortunately once you've eliminate the bulk of your hair tweezing is less painful. Definitely not pain free but I can understand why some guys who've tweezed for a long time don't mind it.
Before I tweezed my head I read pretty much every first hand experience I could get my hands on. There's a yahoogroup that's pretty much defunct now that had a lot of activity around tweezing. Guys stories varied from dazzling successes to abject failure. One of the things I was worried about was am I going to mess up my hair and not be able to keep tweezing. Ultimately I decided the experience of being bald was worth the risk and it worked out alright.