Here's a list of the actors in their age ranges from youngest to oldest, along with the age they'd be by the earliest date this could shoot. (Assuming it starts filming in summer 2024, or the start of 2025)
30s
Tom Bateman: March 15, 1989 (34 now) Will be 35-36 when filming.
Sam Claflin: June 27, 1986. (36 now) Will be 38 when filming.
Oliver Jackson Cohen: October 24, 1986. (36 now) Will /probably/ be 38 when filming.
Christopher Abbott: February 1, 1986. (37 now) Will be 38-39 when filming.
Ethan Peck: March 2, 1986 (37 now) Will be 38-39 when filming.
Tom Cullen: July 17, 1985 (37 now) Will be 39 when filming.
Jonathan Groff: March 26, 1985. (37 now) Will be 39-40 when filming.
Theo James: December 16, 1984. (38 now) Will be 39-40 when filming.
40s
Aidan Turner: June 19, 1983. (39 now) Will be 41-42 when filming.
Ed Skrein: March 29, 1983 (39 now) Will be 41-42 when filming.
Brett Dalton: January 7, 1983 (40 now) Will be 41-42 when filming.
Tom Pelphrey: July 28, 1982 (40 now) Will be 42 when filming.
Jamie Dornan: May 1, 1982. (40 now) Will be 42-43 when filming.
Jack Huston: December 7, 1982. (40 now) Will be 42-43 when filming.
Benjamin Walker: June 21, 1982 (40 now) Will be 42-43 when filming.
Dan Stevens: October 10, 1982 (40 now) Will be 41-42 when filming.
Liam McIntyre: February 8, 1982 (41 now) Will be 42-43 when filming.
Ben Barnes: August 20, 1981 (41 now) Will be 42-43 when filming.
Michiel Huisman: July 18, 1981 (41 now) Will be 43 when filming.
Ryan Gosling: November 12, 1980 (42 now) Will be 43-44 when filming.
Sam Heughan: April 30, 1980 (42 now) Will be 44-45 when filming.
Jake Gyllenhaal: December 19, 1980. (42 now) Will be 43-44 when filming.
John Krasinski: October 20, 1979 (43 now) Will be 44-45 when filming.
Luke Evans: April 15, 1979 (43 now) Will be 45-46 when filming.
Lee Pace: March 25, 1979. (43 now) Will be 45-46 when filming.
Wes Bentley: September 4, 1978. (44 now) Will be 45-46 when filming.
James Badge Dale: May 1, 1978 (44 now) Will be 46-47 when filming.
Matthew Goode: April 3,1978 (44 now) Will be 46-47 when filming.
Josh Hartnett: July 21, 1978 (44 now) Will be 46 when filming.
Jensen Ackles: March 1, 1978. (45 now) Will be 46-47 when filming.
Sam Witwer: October 20, 1977 (45 now) Will be 46-47 when filming.
Michael Fassbender: April 2, 1977. (45 now) Will be 47-48 when filming.
Alexander Skarsgard: August 25, 1976 (46 now) Will be 47-48 when filming.
50s
Bradley Cooper: January 5, 1975 (48 now) Will be 49-50 when filming.
Anson Mount: February 25, 1973 (50 now) Will be 51-52 when filming.
Karl Urban: June 7, 1972 (50 now) Will be 52-53 when filming.
Richard Armitage: August 22, 1971 (51 now) Will be 53 when filming.
Justin Theroux: August 10,1971 (51 now) Will be 53 when filming.
Jon Hamm: March 10, 1971 (51 now) Will be 53-54 when filming.
Nikolaj Coster-Waldau: July 27, 1970 (52 now) Will be 54-55 when filming.
Eric Bana: August 9, 1968 (54 now) Will be 56-57 when filming.
Josh Brolin: February 12, 1968 (55 now) Will be 56-57 when filming.
Guy Pearce: October 5, 1967 (55 now) Will be 56-57 when filming.
Jeffrey Dean Morgan: April 22, 1966 (56 now) Will be 58-59 when filming.
Most likely ones in their 30s In my opinion would be Abbott and Cohen. Provided he can act Tom Bateman, and Tom Cullen. Everyone else has an extremely wrong look for the part for this type of Batman and come across as too similar to Pattinson looks-wise.
Most likely ones in their 40s In my opinion would be Lee Pace, Jake Gyllenhaal, Jamie Dornan, Jensen Ackles. Maybe Huston. Fassbender if they're willing to go older
Most likely ones in their 50s In my opinion would be Bradley Cooper, Josh Brolin and Jon Hamm. Nikolaj and Armitage might surprise too.
Overall I wouldn't be surprised if the screentest shortlist ended up looking something like this: Lee Pace, Oliver Jackson Cohen, Jake Gyllenhaal, Jamie Dornan, Jensen Ackles.
If it came down to 3 I'd say it'd most likely come down to Lee Pace, Gyllenhaal and Ackles.
My top 3 preferred picks would be: Lee Pace, Michael Fassbender and Jake Gyllenhaal in that order.