I see your point.
I would do the following:
Clone my working site (1.9.2.3) to a brand new installation, and do a 1:1 clone. Then try the upgrade there.
Or contact every module/extension company and make sure that their module is compatible with the wanted Magento version.
Regarding the magento developer - try asking around - where are you located in the world ?
-- Best regards --
Kent Christiansen | Magento Certified Solution Specialist