Yes, here's the workaround:
1. Create a standard MaxDiff study using SSI Web. Add a Select-Type question on the same page beneath each MaxDiff question. That Select-Type question is a 1-5 likelihood of purchase question.
2. Collect the data.
3. Create a copy of your SSI Web study using File + Save Study As. Let's call that new study Study2. Edit Study2 to be a MaxDiff Dual-Response None format.
4. Still working with Study2, "trick" the software into thinking you are using paper-and-pencil to collect the data. To do this, click Field + Create Paper & Pencil Interviews. Make sure not to change anything else about your study design so that the software generates the same experimental design as it had used to collect the data. If you are using the standard 300 versions of the design, it make take a few minutes for the paper-and-pencil creation to generate 300 paper questionnaires.
5. Export your Respondent#, Version#, MaxDiff responses, and answers to the 5-point scale questions to a .csv file. You'll be feeding these back into Study2, telling the software that these were actually collected using paper-and-pencil.
6. Put your data in the right format. Using Study2, click Field + Create Accumulated Data Template File... This creates a .csv file with the right labels in the first row so that SSI Web understands the paper-and-pencil data you'll be giving it.
7. Copy your respondent data into the paper-and-pencil .csv template file. You'll be supplying Respondent#, version#, answers to the MaxDiff questions, and also the Yes/No buy responses. This is where you decide what the cutoff is on the 5-point scale for buy vs. no buy. For example, if you think that top box only (5) is a "buy", then you will recode your 5-point scale so that any ratings of 5 become a "1" (buy) and any ratings 1-4 become a "2" (no buy).
8. Import the paper-and-pencil .csv file data into Study2, by clicking Field + Accumulate Paper & Pencil Data...
Then, proceed with analysis with Study2 as usual!