Its called a "re-release/re-dispatch" flight plan; has been in use for years and years. I remember years ago it was the only way we could get the DC-8-61 (sleds, originally built as a 'domestic' a/c), to go westbound across the pond with anything close to a decent load of pax or freight.
Example: going from LGW-JFK, required Dest. fuel, 10% of that, plus 30mins reserve; and can't carry that amount of fuel. Released/dispatched LGW-GDR, with a 're-release/re-dispatch point' just prior to GDR, usually somewhere just prior to 50/50 (50N50W). Just prior to the re-dispatch point, you compute total fuel onboard and contact dispatch; if you have 'min req. fuel' for the re-release, 're-release-Dest.' (now the dest. fuel) + 10% of dest. fuel (now 10% of the fuel req. re-release-dest.) + 30mins, then you can be 're-released/re-dispatched' to Dest. JFK.
Its just a way of playing with the #s, and reducing the 10% required Int'l fuel requirement. Instead of needing 10% of the total dest. fuel (LGW-JFK), you only need to take-off with 10% of that required for LGW to re-release point; and from the re-release point only required to have 10% of that required from 're-release point to JFK'
As I said, its been used for years and still used today. Hope that helps.
DA
P.S. The ETOPS requirements cannot be changed. 180min ETOPS means at any point along the flight, a/c must be within 180mins of a suitable ALT airport. Remember ETOPS means; "Engines Turning Or People Swimming."