Downs has played only a handful of games above A-ball. I think accommodating him in the immediate future plans at this point might be a tad premature.
They could sign a 1-2 year deal to Kolten Wong, Jonathan Villar, Tommy La Stella or Jonathan Schoop and then see where Downs is after 2021. If Downs is still a worthwhile prospect, at worst this would delay him making the team until 2023, with 2022 still on the table.
There are no second basemen on the market right now that should command a deal longer than 1-2 years, except maybe Wong...