My $0.02 is: "I really miss Heathkit". I really love kit building electronic stuff. So perhaps an answer is some "negative advertising" in your product descriptions.
Borrowing on Brandt, hawk1, and Dave4720 suggestions, perhaps something like:
"The xxxx kit from JV Digital Engineering should not be attempted by the novice kit builder.
For successful results, the builder should have previous experience building electronic kits and knowledge of electronic components, and their sensitivities to excess heat and static discharges. The kit builder should have a temperature controlled, grounded tip, soldering iron with a fine tip size, and small diameter rosin core 60/40, or 63/37 or 62/36/2 solder. If these requirements are unfamiliar to you, do not order a kit form of the product.
Kits are warrented for working components and correct component content only.
Completed kits which are non functional may be sent to JV Digital Engineering for analysis. If it is determined the finished kit failure is due to improper assembly, a repair fee will be charged at the discretion of JV Digital Engineering."
Edited to clairify opening statement.