How do you balance building for large potential customers before they buy vs having the sales team sell what you already have?

Rule of thumb: don't build before they buy. If this whale wants something specific, they should put skin the game, either through a services/customization contract or a purchase contract contingent on a feature delivery.

Of course, there's a lot of nuance to a situation like this. 

Maybe there's an obvious gap in the product offering that the competition universally satisfies. It's probably something already on your backlog, and so you know it will unlock multiple incremental sales opportunities by developing it. (Just be careful not to overestimate the ROI on that development; assume the whale deal falls through.)

The more dangerous trap to avoid is mistaking noncommital interest from someone inside that enterprise for a promise to buy. Enterprises have many stakeholders (known and unknown) and even more competing agendas. There are likely multiple reasons that they're not ready to buy, and it's easy to focus on one obvious thing. But it's not the only thing.

If there's really just one thing holding the enterprise back from an otherwise enthusiastic purchase, you and your account team can likely come up with commercial terms to get the deal over the line today with the product on the truck, and a structured agreement to enhance it tomorrow.

Generally, the sales team should focus on selling what’s already on the truck.  However, if there are gaps that are deemed deal blockers for customers, one of the most important considerations is whether the feature being requested fits with the product strategy and is broadly applicable beyond the customer requesting it.  If it is, then it’s more of a matter of timing.  If it doesn’t, then no matter how large the deal is, PMs should be empowered to push back and say no to the request.  However painful it may be to potentially lose a deal, the alternative of building something not in line with the product strategy could end up derailing the product altogether and costing you a lot more than the deal was worth.

Press hard with account teams to understand if the blocking feature is the only thing holding a customer back from signing a deal.  Oftentimes, a single feature is not the only gap.  Also, avoid building a new feature for a prospect.  Ensure the customer is committed before you commit.  In my experience, things oftentimes don’t need to be built before a customer signs, but customers will expect to understand the product roadmap tied to the requested feature.

This has always been a chicken and egg problem, and the challenge itself is compounded by the fact that larger customers demand more scrutiny, (longer sales cycle). 

Depending on the maturity level of your product

- If you are in an early build phase, it is probably worth going down a trial/beta period with a functional PoC built to demonstrate the product.

- However, as the product matures and you onboard more customers, it becomes extremely challenging to entertain such requests, where having a smaller but dedicated solutions team that can work with the customer to steer the requirements according to your product capabilities becomes more and more essential.

Where possible, having visibility into the pre-sales process especially keeping track of features requested in RFPs (Request for Proposals) allows us to be better prepared as a PM overall. This allows us to preemptively keep the most common asks demo ready even though they are not part of your core product.