DRWEL, I will tell you who I had in mind in 1986:
The Queen:  Maggie Smith, Eileen Brennan, Carol Burnett (Paula Lawrence)
The King:  Ellis Rabb, Phillip Bosco (Robert Fitch)
The Prince:  Jimmy Brennan (Reed Jones)
The Princess:  Rebecca Luker (Rebecca Luker)
Mowgli:  Greg Louganis (Davis Gaines)
Eva Standing:  Kaye Ballard (Carole Shelley)
Karen O'Kane:  Pamela Sousa, Karen Ziemba (Alyson Reed)
Eric Dare:  Ron Raines, Howard McGillan (Patrick Quinn)
Those in parentheses did the roles in March 1986.
For 1998, Carnegie Hall, Herb Ross ignored every suggestion I made, except one, which was this cast:
The Queen:  Carole Shelley, Carole Burnett, Maggie Smith (Bea Arthur)
The King:  Simon Jones, Phillip Bosco (Michael Jeeter)
The Prince:  David Elder, Damien Woetzel (Damian Woetzel)
The Princess:  Rebecca Luker, Patty Cohenour (Alice Ripley)
Mowgli:  Brendan Fraser (Bob Paris)
Eva Standing:  Kaye Ballard (Tyne Daly)
Karen O'Kane:  Karen Ziemba, Kristin Chenoweth (Sandy Duncan)
Eric Dare:  Howard McGillin, Victor Garber (Stephen Spinella)
Those in parentheses again did the Carnegie Hall event.  After having to rescore the Beguine for Sandy and Swimming for Bea, I think Tyne was a real surprise, but poor Bob Paris and Stephen Spinella were totally miscast.