To say that there would be no problem with the homeowner's policy is not entirely correct. 1. Depends on how long they stay and if more than 30 days that could be a problem, 2. if you end up having a contract
(which you should) then you are really leasing your property for and in consideration of the "trade lease
hold interest", and that will make it a business transaction requiring a landlord/tennant policy.
If the other people sing the same song as you, you might avoid all that, but if something happens they may not sing that tune. If they lose property arising from a covered peril the property owned by others in your care, custody and controll will be limited....but then their property wasn't in yojur care, custody and control, now was it? So you could have problems.
A landlord policy is similar in premiums to your HO policy, but your belongings may then be at risk.
Best thing to do is to contact your agent and pay any difference to do it right.
Your idea is a good one, if you can find someone willing to play ball with you! Speaking of ball, I'm back to the game