I got Jacks and Red Light Green Light a little further along. COP410 only has 32 nibbles of RAM: each of the 4 registers only has 8 nibbles; 0-7 are mirrored to 8-15. The code was treating RAM as 2 registers of 16 nibbles mirrored to registers 2 and 3. So only 1/2 of the locations could be accessed.

I'm not sure of the best way to do it, but I replaced the RAM_R and RAM_W macros with functions that modify the RAM index for COP410s.
Code
uint16_t cop400_cpu_device::RAM_R(uint16_t addr)
{
	if (m_featuremask != COP410_FEATURE)
	{
		return m_data->read_byte(addr);
	}
	else
	{
		return m_data->read_byte((addr>>1&0x18)|(addr&7));
	}
}

void cop400_cpu_device::RAM_W(uint16_t addr,uint16_t data)
{
	if (m_featuremask != COP410_FEATURE)
	{
		m_data->write_byte(addr, data);
	}
	else
	{
		m_data->write_byte((addr>>1&0x18)|(addr&7),data);
	}
}
Now Jacks seems to run OK, except that I can't pick up the jacks. And Red Light Green Light is better, but the red and green lights don't light up to tell you when to click, so you have to play blind.