I personally believe that Hoid held Adonalsium at the time of the shattering.
I do not believe that he held adonalsium for the power or even chose to hold it, but it was forced upon him and was trying to do the best with it as he could.
when the shattering happened he did was jasnah did and escaped to a different realm eventually coming back to the physical realm, a while after the shattering. I don't think that he wants the power, responsibility or influence of Adonalsium thrust upon him or anyone else.
my thoughts run that his short term goal is to do everything he can to stop odium from destroying every shard and shardworld, and that his long term goal is to stop the force that opposed Adonalsium.
I truly believe more than anything he does not want Adonalsium reformed, he want to create peace between the shardholders and shardworlds before they face the force that opposed Adonalsium. I also believe that he loves the shardworlds and the people that the shards create, and doesn't want to ruin that. I believe that he feels responsible for everything that is happening and will happen because he was the person holding Adonalsium when it shattered.(just my theory)
that is what I believe happened to Adonalsium and where Hoid fits into everything.