Automate Multi User Concurrent Data Loads

We are designing a three tiered system (client, application/web server, database server) that will allow clients through a web interface to select a text file from the operating system and load that file into a intermediate table (import database table). Many users will do this concurrently and data will load into a single table. The text files come in monthly for about 100 firms. No user is able to insert or update the data of another users data (there is a check out system). Their are about 30 to 40 users that will be using the system doing various functions but it is possible for 10 to 20 users to import data at one time. The files can have anywhere from 2000 to 25000 records at a record length of 398.I am concerned about having a good design strategy as well as decent performance.

Problems with each of the Oracle loaders.

1) External tables - Can not read data text files on the application server(which is where they want the text files to go) secondly you cannot create a instance of a external table. Multiple users will be using the external table to point to different text files and loading at the same time.

2) Sqlloader - is mainly a OS level tool and I am not sure how I could programatically point it to a different text file each time a user wants to load. The client will have to have the ability through code to point sqlloader to the correct file name.

I had a creative approach and was wondering if this would work. I would like to use external tables just like a connection pool. I would propose first a scheduled OS job to move files to the database server. I would create about 20 external tables with 20 different directory objects. Using a stored procedure for the user to call and pass in file name and audit info as needed. I would use a Load lock pool table (my invention) to load the name or a code for the external table in use. The procedure loads this code into my load lock pool table when a external table is in use and deletes the name when the load is completed. The procedure would check through a series of if statements whether a particular external table was in use. If in use (exist in load lock pool table) I would check the next available external table until a external table not in use is encountered. Now potentially 20 users at one time but not likely would be laoding into the same table at one time.My questions

1) Could Oracle handle this strategy? What do I need to consider performance wise with the possibility of so many users loading into a single table at one time?

2) Do any of you maybe have another strategy to do this?