I can't help thinking that if you're really serious about using this in an ag application, you simply must stop diddling around with that front caster. No one is going to take that thing serious (at even close to your price point) until you have 4 proper tires on it. Not necessarily "4wd", but a tire at each corner no matter what, even if the front 2 are just steering casters. At least then you would have a tire at each corner for stability over terrain. That 3 wheel thing just says "I'm stuck" even while sitting still. And I would lean towards 4wd as being your only "ag" option, unless it's upgrading to full tracks.
Now for an INDOOR application, warehouse, etc, with concrete floors and smooth solid rubber tires, sure, go ahead and offer a 3 wheeled "caster" variant. Make it a wholly separate "indoor model" if you want. Call it the "Lil' Burro" if you want. Light duty frame, small capacity, and that caster, may not be bad cruising down a warehouse isle, or down a large office corridor. Still don't know about that 5 hr run time. Should be able to run 8 hrs. Most settings have employees that run at least an 8 hr shift, so more "efficient" to have someone stop to plug it in at the end of their "day".
I would also, for an "ag" application, raise the weight capacity to at least 500 lbs, offer it with a powered dump bed option, and maybe a few modular bed designs that can be interchanged on the same basic chassis. Also, just start out with the bigger battery capacity, 10 hrs min run time, 12 would be better.
Then maybe add a "Burro Grande" with 1000 lbs capacity, tracks, 12 hr run time, trailer hitch for a small garden trailer, also powered dump bed.
But honestly, 3 wheels (one of them a small center caster), a 250 lb capacity, and a 5 hr run time? For 5k? In an outdoor ag environment? I just don't see this going anywhere.