Tax treatment of Contingent residuary gifts


I was wondering if anyone could advise whether there are any tax benefits of modifying s31 trustee act to delay the entitlement to income to an age greater than 18 where the gift to a residuary beneficiary (to someone who is not a child of the testator) is age contingent.

It has been suggested that there might be some benefit of doing so for CGT purposes as the gain could be held over but I am not sure on this.

Thank you.