not sure were you live. but for me. here in centeral, IL. they bucket i have on the TLB (tractor loader backhoe) goes a couple inches past each side of the tires. if i had a wider bucket, i would be stuck. i tend to need to kinda bull doze or rather use bucket like a plow for the drive ways and lanes here on the farm. and also needing to lift the snow up into large piles of snow. also needing to dig out many snow drifts. that are 3 feet to 6 feet high. wider bucket would be a down fall for me.
for grass clippings. folks have taken some 2x4s. and a sheet of plywood. to create a large front lip (not sure how else to state it)
if you look at "clamp on forks" that fit over front edge of a bucket. same idea. one 2x4 underneath bucket and other one on top side of the bucket lip. and then screwed or bolted together. and then a sheet of plywood tossed on top.
or just get "clamp on forks" that fit over front bottom edge of bucket. and slide a sheet of plywood on top of forks for grass clippings and brush that you are trying to get rid of.
3pt hitch carryalls kinda same thing. but hook on the back of your tractor. many folks have created little racks to hold tools and other things. will still having a descent size back to toss stuff on to.
if you are trying to clean up your property or doing this as a business. it might well be worth skipping wider bucket all together and getting a *duh* forget name. i want to say "front grabber" that fits over top of your bucket. and it is like teeth. so you can just go up to brush. raise bucket and lower the claw or claws down to pinch / grab hold of the brush then lift the front loader up to pull the brush right out of the ground. and then just carry the crud to some central spot to burn or bury it or what not. vs cutting the brush out, loading and unloading the brush.
3pt hitch rear blade, they are fairly cheap compare to most other implements for a tractor. and can do fairly quick work. if snow is only a couple inches maybe more maybe less (depends on tractor and what you are trying to do)
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everyone has different reasons and even more ways going about something. just saying hey. there might be a different approach that might yield better results in what you are wanting to accomplish overall. if ya gave some more detail in what your projects are, grung duty chore work that you are trying to make easier. folks might be able to point ya in a better direction.
as far as building a wider bucket i am no help there. beyond saying, look up what is available by manufacturer for your tractor, most of the manufactors i have looked at in past year. offer a larger size capacity bucket that is lighter duty. for say mulch. and you might be able to pull some specs as far as width, depth, height, and metal thickness off of.