Q: Can I submit for publication a paper based only on conceptual design?
Can a paper be submitted for publication if it is based on a concept design backed by some mathematical models and simulations? That is, no practical development or experimentation is present. In other words, is an argument based on just mathematical models and MATLAB simulations acceptable as a research article? If yes, would it be worthy of an impact-factor journal or just a low-level conference?
I think what you are talking about is a theoretical paper, a paper that deals only or mainly with the theoretical or conceptual aspects of a research or real-world problem rather than with solutions or applications. To answer your question, yes, there are journals that accept theoretical papers. So, before starting work on your paper or submitting it, you could look for journals that accept theoretical papers and their guidelines for such papers.
However, based on the details you have provided, I would offer a couple of suggestions. If it is possible for you to spend some more time and work on the applications of your design, you could end up having a paper that is more 'well-rounded.' Such a paper may also have a greater chance of being accepted, especially by a high impact-factor journal. If for some reason time happens to be a constraint, you may also choose to work on a conference paper that talks about the theory and some initial or proposed solutions. Based on the responses and inputs you receive at the conference, you could develop this into a full-fledged paper later, again for submission to a high-impact factor journal.
Finally, as you have referred to impact factor and conferences, it may help to go through the following resources for more insights on them.
This content belongs to the Conducting Research Stage