For now, Lewis is thrilled to have Sciver back in the fold in a playing capacity.
"I'm absolutely delighted that she's up for coming on tour and up to the challenge that's ahead of her," Lewis told ESPNcricinfo. "She's a fantastic cricketer, someone who's one of the best cricketers in the world, and to have that sort of quality in your team as far as a head coach is something that is paramount.
"As much as I can get her out on the field and playing her best cricket - and enjoying her cricket as much as anything - I think that will keep her out in the field more often than not, but there is now becoming the question of balance in women's cricket because there is a continual amount of cricket to be able to play if you choose to.
"Part of my job will be around managing schedules and understanding the individual needs of each player, and Nat in particular will be in high demand across every single competition because of the quality that she brings."
Lewis also had a long talk, and walk, with Brunt - he finds the best form of communication is to "get on my feet rather than sit face to face". Brunt is not in the ODI squad for three matches against West Indies but is expected to play a part in the five T20Is that follow and form an important part of England's preparation for the T20 World Cup in South Africa early next year.
"In the immediate future, which is the West Indies tour, we're working to manage Katherine back into cricket," Lewis said. "Then we have a T20 World Cup after that and Katherine is an absolute legend of the sport, she's incredibly well respected and, watching her bowl across the summer, still bowling incredibly well.
"For me as the head coach, that's someone I want around and I want her to be playing as much as much cricket for England as possible. So that's one of the things we had a conversation about on a walk, her plans for the future.
"At the moment she's very much looking in the near future around this tour of the West Indies and then once we get through that, then we'll go again and we'll see where she's at. But at the moment she seems in a really good space and she's been training incredibly hard here… I'm looking forward to seeing her perform at her best in the Caribbean."
"It'd be pretty dumb not to," Lewis said. "He's had an incredibly successful period with the Australian team. I will definitely go and speak to Motty about what he did with the Australian team and the journey they went on and also the areas that they felt they could pinpoint in our group to win games of cricket."
Having welcomed back four players with vast experience ahead of the trip to the Caribbean - 32-year-old top-order batter Lauren Winfield-Hill is in the T20I squad after being dropped during the 50-over World Cup at the start of the year - Lewis also has an exciting bunch of youngsters to nurture.
They include fast bowlers Issy Wong and Lauren Bell and allrounders Alice Capsey and Freya Kemp, who all seized the opportunities they were handed when making their international debuts under Keightley's reign during the English summer.
Lewis said the chance to mentor a group with such a mix of youth and experience was a big lure when applying for the job, which meant leaving his post as England Men's pace bowling coach. He told Jonathan Finch, Director of England Women's cricket, and the ECB's interim CEO, Clare Connor, as much in his final interview for the role.
"There's a really lovely balance of not only age range and experiences but skill level, and different types of skills, and exciting young cricketers who… the world's their oyster," he said. "My job is to is to help those players release their potential and I think that there's nothing that this group cannot achieve.
"My pitch was literally I'm so excited about the ceiling that the players have got, or the lack of ceiling the players have got, and that the team is ready to fly. My job is to almost take the handbrake off and free the players up and get them to play to their full potential."
Valkerie Baynes is a general editor at ESPNcricinfo