I was friend with the #1 player on the open ladder at the time of the standard edition I think (but there has been so many iteration that I may be wrong).
I am not up to date on terminology. What "standard edition" means exactly and what version of Blood Bowl do you have in mind?
The optimal play is obviously to random pick on your linemen until they roll something bad, then fire them. I don't see that not happening in open league.
If you fire anyone who has "something bad", then it's a lottery concerning what you will have (you could end up with nothing), while your opponent will get Linemen with Block at the very least. Yes, it is +20k for each skill, but that's most likely worth it, because it turns a Human Lineman into a
cheaper version of a Human Blitzer. Picking a random skill is still going to cost you +10k and how many of these random skills will be Blocks? Will you have enough random Block to offset the numerical disadvantage? Or will there be enough difference in TV to somehow turn it into an advantage for you (due to having less skills/less pricey skills)?
Consider the following:
1) You can only replace players when you have the money for it. Unless you are fine with playing with Loners (who can still steal the MVP, by the way. If I understand it correctly now dead players can't steal MVP and the MVP is decided on D16 roll).