Once a tree has been reported to you as a high risk by a qualified Arborist, it should be dealt with assoon as possible. That may mean pruning to mitigate the issues, or in some cases removal.
If a tree must be removed and you are open to new ideas, you might consider some form of habitat tree. A habitat tree is a last resort for preserving the habitat value of a tree that is too dangerous to remain. It is created by drastically reducing the size of the crown and installing habitat cut outs for birds, bats, possums, lizards and insects.
Usually habitat trees are either already dead, or are poisoned when the work occurs. Managing a live habitat tree can be costly, and if neglected could cause some significant risk issues down the line.