The wording of your bylaws sounds like it addresses pay for administrative work done by Board members, rather than contracting.  You might want to clarify that, as it sounds like contracting is really the issue.

This is a difficult question.  I can easily see it going either way.  I live on a road that does not have any road association or homeowner's association.  My husband, who is an experienced contractor, has been maintaining and improving the road for the last 53 years, beginning when he was the only one living here.  He began with a discontinued county road that was barely passable by 4wd with a winch in the dry season, and now it's passable year round two vehicles wide.  He knows what he's doing.

Now there are two other year-round residences and two seasonal residences.  The others are mostly grateful and appreciative of the work my husband does, and occasionally contribute to the cost.  But occasionally one of the others (who happens to be the one who regularly complains that the road has not been improved enough) tries to do some road work, resulting in plugging drainage ditches and directing water to flow down the road, causing erosion.  So if those who are providing the work do a good job, their services can be well worth what you pay them, and will likely save you a lot of money in the long run. 

On the other hand, a person who thinks he knows what he's doing (but doesn't) or who has more inflated ego than he has skill, can do a lot of damage.  There should be some way to assure that work is done by someone who has the necessary skills to do it right.  Some jobs, like cutting small brush, may require little skill other than knowing enough not to leave brush where it will clog ditches or interfere with sight distances on curves.  A work day with unskilled labor can be tremendously helpful, especially if there is someone capable of directing the work.  Other tasks, such as grading, ditching, or setting culverts, need to be done by someone who has the proper qualifications and experience to do it right.  

In your situation, where contractors may be hard to come by, if you have a person with the necessary skills to do the work, they deserve to be paid.  Anything from a token of appreciation to a fair contractor's wage would be better than taking advantage of them.  As long as the members have the authority to approve who will do the work, I would be in favor of allowing it.  But I'm sure there will be others who will panic over liability issues.  (There are also liability issues of not getting the work done at all.) It's a matter of weighing risks and costs.  With qualified workers, the risks are minimal.  Even an inexperienced person who thinks can do a decent job.  But the less experience and more bravado they have, the risk increases.  You might want to have a clause about who is responsible for the cost of fixing sub-standard work.