Given the constraints highlighted above, It seems like a venture builder model (focussed on a specific cause area) may be more effective, wherein the following process is repeated:
(1) Generate plausible venture ideas from existing research within EA orgs
(2) Analyze ideas on two dimensions - (a) Cost benefit Analysis (b) Operational feasibility
(3) Incubate and recruit EA aligned technical and non technical co-founders (who then build their own team)
(4) Tie further funding and possibly bonuses to specific short term milestones
Everything above is of course contingent on the ability to actually generate actionable ideas that pass Step 2(a) in a particular cause area.