in my book this is a "it depends" answer.
if the bike is a beater 200s that you just want to ride then by all means weld the shifter on. either mig or tig and then splash it with water to prevent melting the oil seal. in reality you can buy those engines for $50 off ebay and there is no sense in spending big $$$ on a beater machine. buy a whole motor before you spend the $$$ on a single part and then gaskets.
if it is a nice machine then fix it right. a 250r shaft can be swapped in 15 minutes if the engine is sitting on the table. it can be dine in frame too.
so you people need to stop beating on him about it. welding may make sense depending on the machine. inginuity is what keeps these old machines running.