I'd prefer to make EQP qualifying years taper to reflect where the player learnt to play. If you learnt your rugby (13-18) in a country then to my mind you have a much stronger claim than if you moved as a 21 year old professional and simply waited 3 years until you're 24.
So how about you must wait 8 years to qualify but every year under 20 counts double.
Move at 14 and you qualify by age 18 (4 years doubled)
Move at 18 and you qualify by age 23 (3 years doubled plus 2 years)
Move at 20 and you qualify by age 28
Move at 25 and you don't qualify until you're 33 which is the tail end of your career
I’m not sure this would necessarily solves the talent drain that some of the second tier nations experience and if anything threatens to accelerate it as people then begin to scout players at younger ages, to ‘lock’ them in ready for Senior International squads/matches.
It’s an incredibly difficult one to solve.
Whilst we’re on the topic, i’d also like to see the option of young players picked (perhaps 23 and under) for Tier 1 Teams have the option to ‘swap’ back to a Tier 2 Team - i.e. Piutau to be able to go back and play for Tonga, even if it was an amnesty for the new few World Cup periods by World Rugby.
I think if the Islander Teams have some of their players back, they’d be far more competitive - good for the game and good for their own growth and prosperity as they begin to command better match fees, sponsorship etc etc...