Jumbo: As I recall from the ANC passover pay settlement a couple of years ago, the company can train people from different seats at various times without triggering passover. In other words, you only need to be trained in seniority order among those from your former seat also going to your new seat. MEM 30FO to MEM 72FO is not the same animal as ANC MDFO to MEM 72FO. They can train/fill bases as they chose. Check out this language:
Excess Crew Positions
1. Pilots shall be excessed from crew positions in seniority order from among those pilots who bid to relieve that excess. If an insufficient number of pilots bid to relieve a crew position posted as excess, pilots shall be excessed from that crew position in reverse seniority order. Except as provided in Section 24.C.6.b., a pilot who has been excessed, or who has bid to relieve an excess, shall be awarded another permanent crew position in accordance with his seniority and standing bid; provided, however, no pilot may be awarded or assigned a crew position at an FDA base that would cause an excess at that base."
I believe this is the language they use to bypass the passover issue that you are contemplating. I could certainly be wrong, but I think this is the kind of language they used to not pay passover when they trained guys going to ANC who were junior before training senior guys going to Memphis.