E.memoryArea not working on ESP8266 (due to char-iterator ?)

I also believe these is a restriction of 1mb max, and that this is in the espurino core rather than the esp8266 implementation.
Well, it's not a restriction in Espruino itself - maybe just something about getFlash?

I was going by this comment:
https://github.com/espruino/Espruino/blob/master/targets/esp8266/jshardware.c line 48

The restriction seems to be here:

// Save-to-flash uses 12KB at 0x78000
// The jshFlash functions use memory-mapped reads to access the first 1MB
// of flash and refuse to go beyond that. Writing uses the SDK functions and is also
// limited to the first MB.

#define FLASH_MAX (1024*1024)
#define FLASH_MMAP 0x40200000
#define FLASH_PAGE_SHIFT 12 // 4KB
#define FLASH_PAGE (1<<FLASH_PAGE_SHIFT)

Looking at the fetch:

void jshFlashRead(
    void *buf,     //!< buffer to read into
    uint32_t addr, //!< Flash address to read from
    uint32_t len   //!< Length of data to read
  ) {
  //os_printf("jshFlashRead: dest=%p, len=%ld flash=0x%lx\n", buf, len, addr);

  // make sure we stay with the flash address space
  if (addr >= FLASH_MAX) return;
  if (addr + len > FLASH_MAX) len = FLASH_MAX - addr;
  addr += FLASH_MMAP;

So really #define FLASH_MAX (1024*1024) should be determined by the type of Flash chip in the esp8266 board.

https://github.com/espruino/Espruino/blob/master/targets/esp8266/jswrap_esp8266.c

JsVar *jswrap_ESP8266_getFreeFlash() {
  JsVar *jsFreeFlash = jsvNewArray(NULL, 0);
  // Area reserved for EEPROM
  addFlashArea(jsFreeFlash, 0x77000, 0x1000);

  // need 1MB of flash to have more space...
  extern uint16_t espFlashKB; // in user_main,c
  if (espFlashKB > 512) {
    addFlashArea(jsFreeFlash, 0x80000, 0x1000);
    if (espFlashKB > 1024) {
      addFlashArea(jsFreeFlash, 0xf7000, 0x9000);
    } else {
      addFlashArea(jsFreeFlash, 0xf7000, 0x5000);
    }
  }

So this could be used rather than the #define:
extern uint16_t espFlashKB; // in user_main,c