Troposurtfer,
The ICAO requirement you quote requiring 1500ft ceiling for VFR flights only applies within control zones. The logic being that since under ICAO, you may not fly lower than 500ft AGL and in controlled airspace you must be 1000ft vertically from cloud, it would not be legal to depart VFR unless you could both reach 500ft agl and be 1000ft below the cloud. That is ICAO, not UK which does not have the same 500ft ASFC requirement or the 1000ft vertically from cloud requirement in the lower controlled airspace.
Getting back to the priginal matter;
Logically, I think....who in their right mind would depart VFR into such conditions.
There is no reason for not departing IFR. Even if one wished to remain "visual" until a radar service was established, there is absolutely noting wrong with departing IFR but remaining visual...check out IFR minimum height requirements and the exemption for being visual below 3000ft etc.
To look at the situation from a post accident point of view, a review of the decision to depart VFR and then soon after fly IFR would place much emphasis on the prior planning made by the pilot and comparing the actual point of entry into IMC with the planned point of entry into IMC.
Looking the the situation from the "other VFR pilot" point of view........can one honestly say that two VFR flights in such conditions could if they saw each other in good time, manoeuvere suficiently to comply with the rules for avoiding collisions while at the same time remaining VMC?
It is the same as driving down a twisting busy country road at 60mph...where the legal speed limit is 60mph......but one would be deemed reckless to drive so fast.
Regards,
DFC