Hi Fraser
I think you could easily use other veneers for the repairs. I have a whole 14′ dinghy cold moulded in mahogany veneer. But not all mahoganies are equal and agba has particularly good rot resistance.
You can help the mahogany by using a saturating epoxy first (eg eposeal) and/or plenty of thinned and then unthinned primer.
I guess there might be potential for issues from the existing agba and new mahogany reacting differently to heat/getting wet etc, but i would think this a low risk.

Be interesting to hear from anyone who has used mahogany.