I know you have some time invested now with the TL494....but it was designed for voltage mode control. If you want to do current mode, why not build around a more modern IC that was designed for current mode and eliminate a lot of the external parts that you're using?
Well, I was going to use voltage mode. In that context, I opted for TL494 because it's widely available from many sources, it's cheap, and has a high max frequency. For a PSU I'd like it to be easily serviceable for long time. Adding an input current limit solves my OP and this would end the thread.
But since T3sl4co1l suggested building a PSU directly in switching mode, and suggested
average current mode (which I was not aware of), I was interested in learning more about it.
In my current understanding I'm not quite sure of what I'm saying, but average current mode is different from "plain" current mode, for the later there is no ramp generated externally for PWM, as it's generated by the current sensing and "cut" by the voltage control loop. From what I read, plain current mode has several problems (variable slope compensation, noise).
For the avg current mode, there is an external ramp generator as with voltage mode. Thus using a TL494 is not that awkward for an average current converter as it includes the ramp generator (if my understanding is vaguely correct).