So what you want to do is to hairpin the traffic on the inside of the ASA. Inside people will use external ip and hit the inside and the ASA will need to untranslate to the local inside ip and send it back inside.
Well this can be done, but it might have some complications.
You can have the ASA do
static (inside,inside) external_ip internal_ip.
But what is going to happen to the return traffic. When the internal ip responds, is the return traffic going to hit the ASA. If yes, then this could work.
If not then there might be asymmetric routing and you would need state bypass on the ASA so it won't drop packets because they do not follow the state information that it sees for that conn.
I hope it helps.
PK