Square tapper replacement bottom bracket - advice, pls.

Hi All,

I ws searching in the S pages for a replacement for my MTB bottom
bracket, and apparently something like that is only still available at
the Alivio group, and bellow.

Other than being heavier - and how much heavier? - what else bad can I
expect from such part?

Further, probably, the next time I think about replacing a b.b., there
won't be any more square tappered ones in the market, right?

Do I have any way of avoiding this complusory obsoletion, or will just
have to change cranks too (even if I'm perfectly happy with my
cranks)?

TIA,
jbr