As mentioned above, a "thanks but no thanks" response is probably the most likely outcome of going through the trouble to submit your desired improvements to state DOTs. This is not to say you shouldn't do it if you feel strongly about it. But keep in mind why a DOT may not be enthusiastic about your proposals:
Regarding route numbers. By default, state DOTs heavily prefer to keep the status quo in place when it comes to route numbers. While changes might make more sense and make the grid neater, actually changing a route number is a herculean and expensive endeavor. Not only do you have the cost of all the signs, there is the cost of labor of installing all of the signs, and while crews are doing that they're not free to work on other, potentially more important things like replacing safety-critical signage like stop signs, fixing pot holes, etc.
Then, there is the public outreach associated with the educating the public about the change. Businesses along the route may need to revise advertising materials, USPS may need to revise addresses, the word needs to get out to the DOT GIS department, Google, OSM, and Rand McNally... And even after all that the change may fail to catch on with the public. Go to St. Louis and you'll run into people who have no idea what I-64 is, but they can tell you how to get to Highway Farty. And, of course, the DOT is a government agency subject to politics; if a proposed renumbering scheme appears to have no benefit to the public, the DOT will be criticized for wasting taxpayer money, which could jeopardize the jobs of its leadership.
Basically, the DOT view is that unless there is an overriding concern that justifies all of this, route renumbering is to be avoided if at all possible.
New construction and widening. DOTs have a budget, of course. And they also have lots and lots of data on traffic volumes and even destination-origin points of traffic. They use that data to determine where to spend the dollars they have to maximize their effectiveness. Even where there is an identified need for a new construction highway and the funding to build it, determining the best place for a highway is more than you can do at home on Google Maps; it takes a staff of dozens of geologists and engineers to determine the exact alignment for a highway. And even that is sometimes not enough; local landowners can be a feisty bunch, and if enough of them are unhappy with the plans they can be blocked. And, of course, the DOT is a government agency subject to politics; if a DOT tries to build something that appears to have no benefit to the public, the DOT will be criticized for wasting taxpayer money, which could jeopardize the jobs of its leadership.
Speed limit increases. In many places maximum speed limits are set by the state Legislature. In Oklahoma, for instance, state law caps speed limits at 75 mph on freeways and 80 mph on turnpikes. Even if ODOT wanted to set a freeway's speed limit to 80 or even 85 mph, it would be illegal for them to do so. In other cases, local conditions have caused the DOT to lower speed limits, or local residents have even campaigned for them out of a perceived safety benefit. And, of course, the DOT is a government agency subject to politics; if a DOT tries to set a speed limit that the public feels is inappropriate, the DOT will be criticized for risking the safety of the populace, which could jeopardize the jobs of its leadership.
Constituency. How much a DOT will listen to you is, fairly or unfairly, a function of where you live. If you are in Tennessee, Tennessee DOT is, by default, obliged to make at least a token attempt listen to you because you can vote in Tennessee. Therefore, you can exert a small amount of influence over who the Governor is, and thus, who is in charge of TDOT. You are also responsible for paying taxes that TDOT uses to operate, so they have a degree of obligation to you to use that money responsibly.
Other state DOTs have no such obligation. If you can't vote in that state and pay no taxes there, they have no real reason to care what you want. Nothing you can do really carries much consequence to them, so they certainly will not jump to spend millions of dollars on your say-so, unless their data or comments from their citizens are already along the same lines of what you're asking for.