Hi CK,
'Attached is the reimbursement form I spoke of in our last meeting. I think it would be a useful addition to our accounting system as it can serve as an audit and expenditure control device in the future developments. '
Would be indicates 'future maybe'. The sentence as originally written could be interpreted to mean that, or, as a rather less likly but possible meaning, that the form is already in use as part of the accounting system.
In the future developments is an awkward phrase. I'd recommend omitting it or saying it in some other way.
Best wishes, Clive