Here's what I told my client:
It is not clear whether FDA will accept a 510(k) that claims substantial equivalence to a 510(k)-exempt device. The guidance on its website for selection of a predicate would seem to indicate that it will:
“…any legally U.S. marketed device may be used as a predicate. This includes: a device that has been cleared through the 510(k) process; a device that was legally marketed prior to May 28, 1976 (preamendments device); a device that was originally on the U.S. market as a Class III device (Premarket Approval) and later downclassified to Class II or I;
or a 510(k) exempt device.”
Find and Effectively Use Predicate Devices
This information is identified as current as of 2018. However, FDA's 2019 refuse to accept checklists for 510(k) submissions seem to identify 510(k)-exempt devices as inappropriate for 510(k) submissions:
"FDA staff should determine whether the 510(k) submission is for a device type for which 510(k) is known to be an inappropriate regulatory approach, such as when the device type is Class III type and a PMA is required,
or the device type is Class I or II and 510(k)-exempt."
For Elsmar Cove, I will add:
Of course, the latter is "just a guidance," that contains "nonbinding recommendations," so I'm still inclined to think that FDA can if it wants to. I doubt it would want to most of the time, unless it saw it as minimal work for a filing fee. I think it is unlikely to think the work will be minimal unless the 510(k) were submitted by a firm that has established a good track record with FDA. Another kind of "clout."
My client had no track record with FDA, so I told them I thought it was highly unlikely, but that I'd be happy to ask. They decided not to.