Second, you should win deals quicker. Less time waiting for a customer to perform their own evaluation or check technical capabilities themselves, or having to pay for people to help them. There should be quicker responses to difficult questions
Thirdly, you should get out of unwinnable deals quicker. Don't waste time trying to sell to people who can't use your product, qualify out earlier and without committing to too much work. This area can be a trap, as sometimes you spend a lot of effort trying to win unwinnable deals, but if you qualify out sooner, you spend more time on the things you should win. These prospects still might be useful long term, but you should nurture them with marketing and PR until they have a viable opportunity to engage.
Finally - you should win deals for higher value than before. This could be all at once, or in future phases, with increased cross selling capability. It could also be just a more value based approach at seeing how much better the product, service capabilities are, and how they generate value for the customer.
Sales engineers have several ways of ensuring direct value to the sales organisation. I've focused on these direct points of value here, but your presales organization could also add value via support of marketing & customer success as well, and they should be feeding back valuable insights to engineering too.
The amount of value here should be measurable and benchmarkable on a per-sales rep and on the overall cost of sale and the margin on the sales operation. If your organization sees further potential gains in these four areas, that could mean that increasing the relative size of the presales organization could further leverage the sales team.