I'm very bullish on all 3 of the GWS mids that you listed, Kingsley was the midfield/stoppage coach at Richmond and I would be gobsmacked if doesn't play those 3 as the 1st midfield rotation.
I get your point about being hesitant in loading up on the forwards, but I think comparing last year to this year carries assumptions that possibly aren't relevant.
I assume that your 5 starting keepers last year included Cogs and Brodie, maybe F4 & F5? Those 2 cost a combined 477k and delivered an average of 203 between them. My guess is that those who started them were hopeful that they would be good stepping stones, the fact that they proved to be keepers was a huge bonus, both in pts for their positions, the money saved and then spent on a better starting side combined with the added value of at least 4 trades saved in upgrading them. A very small price to pay for a lack of flexibility, hell hindsight says that Brodie should have been flicked for Parker at his bye who averaged 10 PPG more for the rest of the season (just an example).
As you highlighted, all of the 4 mentioned for this year have durability issues (as well as say Fyfe & McLean) I would think that the chances of 1 of those 6 going down in the season is extremely high, I can see a revolving door scenario being a real possibility. What I don't see however is Fyfe and McLean becoming keepers, there is a world where it could happen but the chances of both happening are extremely thin, obviously a huge win should it eventuate.
Cogs, Rozee and Taranto each share the rnd 15 bye and one of them could be sideways traded to someone who has gained DPP. So I think that the flexibility issue could be a bit overplayed, if we do end up that way then it's because 2 x cheapies became keepers and I'll take that everyday.