Your specified needs indicate a lot of future excavation/landscape work. Until this last year those were the predominant uses that I have had compact utility tractors for. Having had the only Cut with a small backhoe on an island in Alaska for a good many years, has shown me the ins and outs, do's and don'ts, capabilities and limitations of these small tractors. Especially in regards to excavation work.
Lets start out with loader requirements. You already stated the need to be able to load over the side of a small dump truck. Minimum side height say 80", to be able to load to center add at least 12", now your talking 92", 100" would be better. Second a heaped 60" bucket of sand or some other dense material and your talking close to 1000lbs or more. Anything smaller and your talking increasing your amount of work time many fold. Also make sure you get a heavy duty bucket, standard buckets are easily turned into a pretzel. then you need a tractor with enough frame weight/size to handle that type of load. Yes you can always add more weight, but will the axles, loader mounts, etc handle it. As well as the hydraulic source. Also with a 4n1 bucket a loader with a 1000lb minimum lift capacity should be considered to compensate for the weight of the 4n1 bucket.
Under attachments you show BH, I'm assuming that to be a backhoe and not a brush hog. Most tractors in the 29/30 horsepower have enough hydraulic power and weight to handle a good 7.5' subframe mounted backhoe easily. you can put a small backhoe on a smaller tractor, but you will shake the tractor around an awful lot, its limited. Also for strength and longevity I would suggest a subframe mount.
Now if BH stands for brush hog, then the question is how big? Under 25 pto hp I think your looking at 48". Over 25 pto hp well then probably 60". It depends on what you have to maneauver around and how fast you want to cut. as well as the cutters extension beyond the width of your rear wheels.
For finish mowing I think you could add about 12" width to the above hp requirements.
You didn't mention if you would be comfortable with a gear tranny or a hydrostatic transmission. Something important for your decision.
Now this is just my opinion, take it as you please. I think your looking at tractors that are to small for your needs. My suggestion would be to look into the @ 30 hp range. The kubota B2910 although powerful enough may be limited as your loader lift hieght and max weight lift capacity. The L3010 and possibly the L3000DT might be better. Also the New Holland TC29's and TC33's as well as thier economy model TC30's would be ideal. Then there are some makes like Kioti, Branson, Mahindra and Long that are making some very strong tractors these days.
I for one went with a New Holland TC29 this spring. Size weight and power it is ideal for my needs, which match many of your needs. I did however go with an aftermarket Woods 1012 loader, for more max weight lift capacity (1200lbs versus 850lbs) and a matching tried and true Woods 7500 backhoe. Altogether this seems like it would be an ideal pkg for your needs also.