Seems OK as a logical pattern. But, as always. the devil is in the detail.
This all hinges on the implementation of your Services use of COM components and specifically the COM components handling of threads. If your COM components are thread-safe and marked to use an MTA (Multi threaded apartment) you should be OK. However many COM objects are marked as STA (and so use the Single Threaded Apartment)
In relation to "is this okay performance-wise?", then if your COM component is an STA (which it will be if it was created in VB 6.0) you will have to do a bit of thread untangling (otherwise all your service requests will queue up and performance will get worse under load.)
This article explains both the problem and the solution to this (for ASMX services)...
http://msdn.microsoft.com/en-us/magazine/cc163544.aspx
..and solution if you're using WCF services...
http://blogs.catalystss.com/blogs/scott_seely/archive/2007/09/27/203.aspx