can a implement also be a magical item with their own activation
such as wand implement also being a wand of soothe
or a regalia implement that are also a staff of power
I don't think so.
Choose an implement from the options to which you have access. You begin play with a mundane item of that type
Part of the design of Thaumaturge is having the character balance and juggle the various items that they want to have in hand. Combining them together defeats that purpose.
and can a staff be used as weapon implement
other specific weapon can be so staff should be able to be
A staff, yes.
A staff, no.