It should be either the Daihatsu Mira or Mira e:S.
Daihatsu has been well known for its impressive ability to 'dig out' as much space as possible for the cabin within the smallest footprint for its models. Mira and Mira e:S are some of the examples. Although the wordings are in Japanese, we can understand what they mean by looking at the dimension lines and values. As comparison, Viva's cabin space is measured at 1845mm (length) x 1300mm (width) x 1250mm (height).
Mira's (top) dashboard looks dull compared to Mira e:S (bottom). Hopefully Perodua will have a new dashboard design if Mira is used as the replacement model of Viva.
Most important would be the pricing of the replacement model of Viva. Since the Proton Saga SV has been priced closely to the current Viva, Perodua has to set the price of the all-new Viva carefully. More standard equipment and safety features would attract more buyers, especially the young ones.
*Thanks for reading! Like my page at SimonHar.com and subscribe SiMon HaR_!