Posted:
Your Bylaws might allow the board to enact rules, as long as they don't override the CCRs - take a look at yours (Bylaws generally dictate how the association is to be run, such as listing the powers of the board).
If they can issue additional rules, that's usually done to flesh out the CCRs. For example, the CCRs might say exterior changes have to be pre-approved by the board, but the board could issue policies on what information needs to be provided, the appeals process if the request is denied, etc. In your case, you may feel these rules are more restrictive, but do they stop people from submitting requests in the first place? In my opinion, no. You also say the CCRs are silent on some issues, so you might find yourself in a circular argument (show me where the CCRs limit exterior change applications for only one year - no, YOU tell me where they don't).
All of that said, here's one person's opinion on your examples:
CCR applications are only good for one year - I think that's reasonable. It's better for you to get your plans in place along with the vendor so you can provide all that information in one shot when you file your request. If something happens where the project might be delayed (e.g. certain materials are back ordered), what's wrong with the homeowner keeping the board informed so people don't wonder why you've had a half-built fence for the last six months? That could be why some people are now finding their requests may be rescinded. Personally, I say they have to explain the reason(s) for the delay - if they can't or refuse to, I might rescind the approval or give them 30 - 90 days to either finish the job or restore the area to its original condition. What happens between them and the vendor after that is their business.
Considering visual impact on members for who the completed project will be visible - that sounds like a long-winded way of saying the change could be denied if the neighbors don't like it. That's too subjective - the current neighbors may be ok with the change, but then they move and the new neighbors absolutely despise it and start making noises to you and the board about moving it.
Consider anticipated futural visual impacts on the value, desirability and attractiveness of the project - I agree with you this is entirely too subjective, especially the "value". People can't even agree on what makes up property values and tastes, materials, designs, colors, etc., can all change over time. I think there can be reasonable rules on things like color because some of us really don't want to live next door to or across from a purple house {even though I'm a Prince . Rules on accepted materials could also be reasonabile - for example, we have a lot of wooden privacy fences in my community, including moi, and some of them haven't aged well {including moi}). If I were on the board today, I'd be asking about the type of wood being used to build the fence and how it should be maintained because the homeowner might not be aware of that. It might be easier to push for a vinyl fence because they're pretty maintenance-free, limiting the colors to white or some shades of brown or gray.
But that's MY opinion. Get the wrong people on the board and you end up with endless arguments about style. It may be better for the board to run a poll asking people their opinions on design standards - what exterior changes require them as opposed to something else? Perhaps have some landscapers or outdoor equipment vendors walk the community and make recommendations - not that you want cookie-cutter houses, but maybe some people need to be told a treehouse isn't necessarily a good idea (might damage the tree, attract termites that can spread to neighboring homes), or some trees may look pretty, but are really invasive species and should be avoided.
If it is not right do not do it; if it is not true do not say it. Marcus Aurelius