I am not an attorney and recommend that you run what follows by an attorney with experience in using the Maine Private Ways Statute (Statute), 23 MRS §§ 3101 - 3104.
I believe your concerns above can be addressed by now adding a statutory component to your current road association. By-laws are not essential. All property owners along your road will become members of the "new" statutory association.
Keep your current non-profit corporation road association and make it a statutory association by using § 3101, subparagraph 2, Call to Meeting as outlined in Roberta Manter's "Statutory road Association - Warrant for First Meeting" on our Resources Page. Follow the Statute to the letter. You must notify all owners along your road by USPS at least 30 days prior to the meeting.
I would also vote to reaffirm your non-profit corporation at this meeting. You will become a statutory road association if the items on the Warrant are approved by majority vote. If you continue to use the Statute to call and conduct meetings, you will be able to hold owners accountable under § 3104, Penalties and process, to pay their share of maintenance costs or be subject to a Notice of Claim against their deed in the amount of their delinquent maintenance fees, late payment penalties, costs of collection, and related attorney fees.