O'Neill and his chief scout Ian Storey-Moore watched the Welsh international on several occasions last season.
Koumas has stated his desire to return to the Premier League after Albion failed to gain promotion from the Championship at the first attempt.
The Baggies have already rejected a joint bid of £5million from Birmingham for Koumas and 23-goal leading scorer Diomansy Kamara.
But O'Neill is understood to be prepared to allow one or more of his fringe players - possibly central defender Gary Cahill and midfielder Isaiah Osbourne - join Albion on loan as part of the deal.
Both players figured in the first-team squad last season at Villa but may struggle to play a prominent part in 2007-08 if the expected influx of signings arrives at Villa Park.
Cahill lost his place to Martin Laursen once the Dane gained full fitness after his knee problems and he formed a solid partnership with Olof Mellberg.
Osbourne is highly regarded by O'Neill but is more a player for the future and the expected arrival of Nigel Reo-Coker from West Ham would see him slip further down the pecking order.
O'Neill is hoping to conclude the Reo-Coker deal before Villa report back for pre-season training on July 4 - if they can reach a compromise with West Ham over the fee for the England Under-21 captain.