1:1 isolation transformer fuse on secondary side - an option?
If you move the fuse from the primary side you have no protection in case the insulation of the primary coil of the transformer fails.

Maybe the best solution is to have a fuse on each side:
e.g. 2.5 A on primary and 250mA on secondary. 

BTW a fuse is not enough to protect against electrical shock.
Something lika a RCCB (inserted on the secodary side) is needed for an effective protection.