I'm a sucker for strict rules, but it's difficult to take all possible scenarios into account before they happen. This is one of the reasons I don't actively offer escrow services (although I've done it a few times when asked). Yahoo62278's suggestion is a good disclaimer to add if it happens again.
Definitely, covering all possible scenarios is a very difficult task but at least covering 95% is already a benefit. Even if it takes some time to figure out how to do it because we'll always have a learning curve.
Maybe every project doing a Signature campaign can provide an escrow fund and in case of an exit scam, losses could be covered.
Eddie's post comes to mind again:
Should never have put the temporary illusion of safety above personal liberty..
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This forum started acting like protecting idiots is more important than letting users express their free wills..
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A new startup can’t come here and start a signature campaign for example without completely being bullied into “trusting” some escrow they have probably never heard of, so heaven forbid they couldn’t possibly scam some users willing to take the risk..
What eddie13 said there, sounds good but doesn't work in reality for most cases. And nobody gets "bullied".

Yes, services should be able to decide which way to go - but some ways will end in a big mess.
We have seen that for signature campaigns managed in-house, like YoBit or right now 1xbit and the result is not desirable.
Bitcointalk recommends to select a trusted campaign manager to avoid spamming the forum due to Shitposts or similar issues. No one complains that selecting a campaign manager is something bad or services are getting "bullied" to select a proven campaign manager.
Selecting a know campaign manager is beneficial for the service, the forum and all participants.
Same applies to arrange an escrow fund.
Of course, providing some BTC into a trusted escrow for signature campaigns should be voluntarily - and will very likely attract more participants compared to a competitor, where no such escrow fund is offered.