One possible solution is to pad the numeric values with a character in front so that all are of the same string length.
Here is an example using that approach:
select MyColumn
from MyTable
order by
case IsNumeric(MyColumn)
when 1 then Replicate('0', 100 - Len(MyColumn)) + MyColumn
else MyColumn
end
The 100
should be replaced with the actual length of that column.