For instance, like other big non-profits, EA orgs might want to hire institutional fundraisers to tap into larger grants from big foundations other than the usual suspects

I've looked into this a few times and it does seem like it will become a promising channel. In particular from the big donors that do very large checks (>$500k). At least one org I know is experimenting with hiring a full-time grant-writer. I currently think it won't work well for most EA orgs for some time to come.

Worth noting that most big foundations have large sr. management time overheads and often require designing bespoke projects just for that foundation. Grant-writers also generally have slow payback periods (>1-2 years not rare, more if first one doesn't work out), are very tricky to evaluate during hiring and expire once you run out of foundations / major donors to apply to (most don't do much repeat funding). Not insurmountable challenges.

An alternative is to hire one-off fundraisers who approach lesser known major donors for you, I think that may be promising but requires a large time investment to train that person to talk about your charity. They also still require a large amount of Sr. mgmt's time (non-foundation major donors will generally want to speak to the founders and most those conversations will end up being a no) and are more likely to generate one-off funding rather than repeat.

It may be that expanding philanthropic advisory within EA in general is more promising. Whilst not specifically focused on raising funds for EA orgs, an increased number of smart and best-arguments-aware donors in the space in general could well have a similar result for less sr. mgmt time cost.

It could also be that having a semi-centralised fundraising team that manages a team of generalist fundraisers that are shared and specialist fundraisers that each work for a different large EA org could work really well. Train them all up in tandem and work out how to evaluate them, focus on >$300k checks from major donors but also have a grant-writer or two shared between them, hire most talent from mainstream pools, etc., We looked into something like this to function across all the GiveWell charities but it ultimately looked like it wouldn't work.

It doesn't seem unlikely that that last option never makes sense, because by the time you have orgs large enough to justify the above ($5m-$10m pa), those orgs also organically start to hire their own internal fundraisers and grant-writers just to meet their large budgets.

Looking forward to putting more thought into this.