Since flashing the kernel takes about a minute you can just flash the kernel (and reboot) and then see if the hotspot backend still works, if not then it's tough luck.

AFAIUnderstand the "first" OC kernels were using exactly same config as stock (except obviously for the clocks) and thus do not have NAT. But I have lost track of which kernel has which features... (for example my hotspot kernel has only NAT and QoS in addition to stock, titans kernel-maemo has a ton of generally usefull features)