Rivera is a bit of a gamble. He hasn't really shown anything but glimpses of hope in traditional races. Digging up in his results, except a couple of notable placings (9th in Milano Torino against Top competitors and a 5th place in a MTF in Vuelta a Burgos), all his results came in asian and eastern europe races, so there is a huge question mark on him.
However, I agree for the minimum wage he would be a good recruitment for Spanish Pro Conti Teams.
Vacek is certain to find a spot for 2023. The italian riders of Rusvelo, especially Fedeli and Malucelli should be nice additions to any italian PCT. Scaroni, Carboni, Conci and JM Diaz could range from good to decent mountain support for WT teams short of manpower.
Zakarin, despite his notable decline, deserves also a farewell on the roads.