Thanks a lot for you comment.
The reason why I haven't used SQL job agent is because this solution has been implemented for a client using SQL server with a limited permissions. They can't schedule jobs. Moreover there is a lack of technical / admin skills within client's environment. So they simply use our data warehouse front end to do all required admin stuff. When they need to execute SSIS or a job they do it via front end application.
As much as I agree that front end should be changed in a way that you've described (if needed run SSIS via SQL agent with 32bit settings enforced, probably additional tick box on already existing form) but changes to the product take time. They need appropriate design, approval, QA ETC).
Also I’m not sure if I would like to ask our customers (often with minimal tech skills) to choose if package is 32 or 64 bit as they wouldn't know it. Knowing life, everything would be executed in 32 bit mode – just in case:)
The idea is that whatever SSIS package they are going to throw at the system it should work. Number of customer support calls, involved investigations should go down.
But all of this as I've mentioned above: when there is a lack of skills and you want to cut down on support.
I hope I have explained reasons behind to your satisfaction.