Have you tried Dynamic SQL? In a hurry but I threw this together.
DECLARE @test-2 TABLE (SomeValue INT)
INSERT INTO @test-2
VALUES (2000),(2001),(2002)
SELECT * FROM @test-2
DECLARE @maxValue INT
DECLARE @sqlstmt NVARCHAR(200)
SET @maxValue = (SELECT MAX(SomeValue)+1000 FROM @test-2)
SET @sqlstmt =
'
CREATE SEQUENCE test_seq
AS INT
START WITH ' + CONVERT(VARCHAR(10),@maxValue) +
' INCREMENT BY 1
MINVALUE 1
MAXVALUE 2147483647
CACHE
'
EXECUTE sp_executesql @sqlstmt;
SELECT NEXT VALUE FOR test_seq
SELECT NEXT VALUE FOR test_seq