Hi, I've read the various threads and very detailed guides on these different vouchers, and I think I understand what can and can't be done, so just looking for confirmation that what I intend to do is valid. Have tried to lay it out logically and clearly.

Destination is Tokyo Haneda HND

Three people to be booked for, me, friend A, and friend B.
All Avios and vouchers will be associated with my account. No friends and family account involved.
Outbound flights originating LHR, BA codes on BA metal.
"Straight" returns rather than open jaw, again, on BA.

Companion voucher to be used for my ticket and friend A's Avios tickets, both return. Combined with a GUF2 to move up from business to first on both tickets for both outbound and return.

Barclays "upgrade" voucher to book return for friend B in business while only spending PE Avios cost.

High-demand route, so will need to be a midnight phone call 355 days out for the outbound, then the same for the returns.

Reward availability in first NOT needed to apply the GUF2 for me and friend A, only "class A" discounted first revenue ticket availability, even though the underlying companion voucher booking would be an Avios one.

GUF2 being earned by tier points from a holiday that ends a couple of days before the 355 days out date - it's entirely possible I won't yet have the voucher in my account and ready to go when I need to book the outbound flights, as the bonus TPs from the holiday could take a while to ping through.

In that event, I understand can book the tickets for me and friend A in business, and then phone up again a few days later when I have the GUF2 and apply it to move up to first with additional cash element.

With all the outbound flights booked, at 355 days out from our intended return, I can phone up and book the returns, and ask them to be associated with the relevant outbound bookings and vouchers.

By my maths, if it's 100k Avios each way for business and 50k each way for PE, I need:
Outbound
100k for me
0 for friend A, as the companion voucher removes the second 100k cost
50k for friend B, as it is upgraded from PE to business by the Barclays voucher.
Return
100k for me
100k for friend A
100k for friend B

And then when the return bookings are associated with the outbound ones and their already-applied vouchers, I would have 150k Avios refunded from the return booking. I don't mind if this takes a few days.

I may well be able to book the returns just for 150k all in on the phone right off the bat, but as long as I have 450-500k Avios "on hand", I should be covered for the potential worst case scenario.

Have I made any massive howlers in the above plan?
Anything I'm forgetting? Yes, I'm aware from previous conversations that the business to first GUF2 cash component may be a bit hefty to to lack of RFS pricing in first.
Is there a way to see whether those first "class A" fares I need for the GUF2 exist on my chosen flights?
How much polite steering of the conversation with the BA staff on the phone is likely to be needed to make this happen without being rejected as not possible? I'd like to avoid things like "needs to be reward availability to apply a GUF2 to a reward flight" and so on.