As I said in your Abu thread, there are usually several good ways to solve a Pharaoh problem. There isn't a "right" procedure for Meidum.
Many players put the pyramid complex in the south. I put it in the north (with a long causeway), close to the rocks (where quarries are) but otherwise out of the way. (I crossed the river in the middle of the map--if you cross the river in the north then putting the pyramid complex in the north might be troublesome.)
If the largest monument can be placed at the start of the mission (as is possible for pyramids and mastabas), I recommend doing so. This prevents you from building something else where the monument should be. The only reason (that I can think of at the moment) for not placing the largest monument immediately is if you have decided to build another monument first.
At the start of a mission, instead of thinking about satisfying requests, I recommend that you concentrate on making money, feeding the people, and (in some missions) defending the city. After those, begin monument construction. If you're producing several expensive exports, feeding your people, and building a monument, you will probably be producing whatever goods are requested. If a request happens to be for something that you're not already producing, then you'll usually have enough time to produce (or buy) it.
Papyrus is a good (expensive) export, even when reeds are imported. However, wood is even more expensive, and a wood industry is inexpensive, uses few workers, and starts very quickly. In most missions where wood can be produced and sold, it is the best first export. Meidum can also make good money by selling pottery, bricks, and linen (from imported flax).
I don't know if an archer fort will be sufficient to defeat the Libyan invasion--it might depend on the difficulty level. Archers are lousy at hand-to-hand combat, so I recommend having at least some infantry as well. Infantry are expensive, since the weapons that they need require imported copper, but Meidum can make a great deal of money from trade.
It's OK to delete any or all of the Kingdom road. Just make sure that there is a path from the entry point to the exit point--if you block the path then bad things will happen.
You don't need to import fish, unless you want houses that are better than common residences. The Prosperity requirement is only 25, so there is no need for better houses. I wanted to get Prosperity 100, which requires some scribal housing, so my Meidum imports some fish for a few manors.
A housing block is simply a combination of houses, roads, and buildings that provide services to the houses. Some players use "standardized" housing blocks, others (including me) design new housing blocks for each mission. To build (or insert) a housing block, look at the design and build roads, vacant lots, and buildings appropriately.
The Mission Editor is used to create custom missions--it cannot be used to play a mission.