It sounds like overkill. It is no problem to replace an old style terminal that displays characters coming over an RS232 interface. You just need a PC with a terminal program, such as Hyperterminal, or whatever the Linux equivalent is called. Unless I am misunderstanding your requirements hugely. Any old 486 or less PC that someone will almost pay you to take away will do it.

(Serial ports and monitors are more future proof than you think ... at least for now ;-)