Watkin made 77 not out on her T20I debut and 62 on her ODI debut - both against Ireland - with the second knock part of a record total of 491 for 4.
Bezuidenhout, who played for South Africa Women in 2014 and 2015 before switching over, made her New Zealand debut in the same game, hitting 23 not out off 15 balls.
"It really is a dream come true to be offered my first full-time professional contract," Watkin said. "Getting a taste of international cricket in Ireland and England left me wanting more and it's awesome that I'll now be able to train and play all year round."
The 20-year-old Watkin and the 24-year-old Bezuidenhout are among four new players in this year's list of 15, joining Canterbury Magicians allrounders Hayley Jensen and Kate Ebrahim, who made comebacks to the team this year. Jensen, 25, had last played for New Zealand in 2014, while Ebrahim last played an international game in 2015.
The ones who missed out after being on the list last year are Rachel Priest, Thamsyn Newton and Anna Peterson, while Erin Bermingham has retired from international cricket.
Priest is the senior-most player to miss out, having played 86 ODIs and 68 T20Is since her international debut in 2007. She has had somewhat lean returns in the last two seasons though, with 440 runs in 19 ODIs at 23.18, though her strike-rate of 84.13 remained healthy. She wasn't picked for any T20Is in 2017-18, but in the four T20Is she played in 2016-17, she made only 45 runs at considerably slower than a run a ball.
The players who have been offered contracts have until August 6 to accept the offer.