It would not be the first time I've seen hw & sw manufacturers doing a poor job.
Anyone who owns an N900 probably knows that, we tweak almost every component in the system and improve it.

I hope, besides all the people explaining why it can't be done, there would be someone explaining how it can be done.

I want to tweak the phone into thinking the signal is slightly larger, not to rewrite the modem code.

This is hopefully doable.

If you look at the settings of most transmitters (look in your wifi router setup), this is usually a free parameter. you can have more power in broadcast and less retransmissions of data, or less power at broadcast and more retransmissions of data.
There is an optimum, which I am not sure Nokia found.