Indeed, bridges should be seen as "unbreakable doors/temporary walls" first and a way to cross chasms second. I often have 10+ bridges and only 1-2 actually serve as bridges
Seriosly though, why do so many graze on the surface? There is this stuff called cave moss that vigorously grows on (easy to dig out) underground dirt. You dont even have to leave caverns open. Breach them quickly so you know where it is (for fortress planning) then wall off that opening. Dig out your underground pasture and the moss begins growing immediately! No need to deck over giant areas, build walls, or ever worry about trolls eating your mutton!
As far as fortress planning... yeah, that layout is horrendously inefficient. Workshops tend to create groupings or chains. Farm->(textile plants stockpile->)farmers workshop->loom->(mill->)dyer's shop->clothiers shop is one of the more straightforward ones I put in an actual line. The dyes/queern/mill I put to the side of the dyer's shop (that is sandwiched between the loom and clothiers). Workshops can actually serve as stockpiles if there is no valid ouput for their goods and dorfs will seamlessly take from them. So my weaver raids the farmers WS for thread while the dyer raids the loom for cloth (and then takes 2-3 more steps to the mill for dye). If one step gets too far ahead, that shop will get cluttered and slow down- this actually helps to balance the chain. Additionally shops can be added to the sides as well. With current barrel-related hijinks, this is definitely the most efficient set-up.
Animal processing tends to be another floor. I have a bone pile on one side of the butchers with a (bone) craft shop and bowyer on the other. The meat stockpile is usually directly above to sit next to the kitchen and plant stockpiles (which are fed by the farms on the level above THAT, so two over the underground pastures/animal training zone). The dining room will also be on the same level as the kitchen (over animals and under plants). I tend to put my tannery touching the butcher's shop to help make sure the raw hides don't rot, then a short distance from there I have a leahter stockpile (most of my leather is bought, honestly) near a LW shop. If I have shearable/milkable critters, I add farmer WS in the pastures with small SP's sent to give to the main ones further inside.
This is another handy tool- relay stockpiles. You can have a main stockpile somewhere convenient, and then set it to give to a very small (under 10 spaces) specific stocpile (say, featherwood only) near a WS. This is how you force the crafting of specific resources. They can also be used like I do with the pastures to connect resource acquisition from different sources. I often have several just for plants. One big stockpile for getting plants out of the fields that links to several smaller ones directly adjacent their WS. Brew plants to the still, Quarry bushes to the farmer WS (NOT) the one in the pasture!), mill plant next to the quern, etc. You'll want multiple craft and farmers WS- they have far too many uses to rely on just one of each- add extras near each chain as appropriate.
Another place I make use of relay stockpiles is for wood. Wood stocpile is my first floor to prevent wood haulers from dragging too much. I tend to have a huge (10x10 at least) wood stockpile just to get the lumber safely inside. However, it wastes too much of my carpenters time dragging logs from the back of this pile, so I set up another SP sandwiched directly between the giant log pile and the carpenters. This keeps my legendary bed maker from having to move much while forcing the scud-monkey cheesemakers to ever haul the logs closer. There are wood furnaces off to the side with a small charcoal pile. This pile is linked to a larger charcoal pile down by the mines and forges- its easier to move the charcoal stacked in bins than it is to haul wood down or bars/ore up. I then place a chain of wood burner->lye maker->soap maker for when I have to do that crap. A wood-craftWS will also be adjacent to the carpenter to churn out pots or other crafts. I never make xbows from wood- it has far too many other uses compared to bone.
There is another layer for my various furnaces, and another for stone+jewels+mechanic (similar set up to the wood pile) With all these and 2 layers for bedrooms (at least, it's too much horizontal space to put 200 rooms on one level) and usually an entire floor for dining room+kitchen+hospital, I tend to have a fort of about 8-9 layers not counting the surface (usually just a token structure til lI get around to building the courtyard). Quite simply put, you aren't playing DF right if you don't make proper use of vertical space. Dorfs move diagonally at 1.4 times as fast as they do cardinally, but they will still push a minecart filled with lead up a ramp as fast as they'd walk down one carrying nothing but a tune- you need to utilize this! Even if you don't make 5 layers of various connected workshops, you can place the workshop stockpiles directly underneath their paired shops. Think of them like storage basements... so next to your mason is a staircase leading down into your stone stockpile. I tend to find putting all the stockpile's on one level to "see everything better" to be missleading. Sure, you see your dorfs scurry around... but this still doesn't tell you much. For the "big picture" it helps to get used to the manager and stocks screens. Relying more on these will make it easier for you to give up "seeing them all at once" and break up your workshop level into more efficient chains.