Bob, the EZJack I linked above has a 20,000 pound rating and is what the USCG specs for their small boat trailers.
The advantage to using one of these is that even if it does not lift the trailer high enough to remove the tire, you will have that much less to lift with a jack.
Electric impacts - if you are going to spend the money on a cordless electric I would consider one strong enough to remove the highest load lugs, most likely your truck. My truck lug nuts are torqued to 165. And a "300" pound rated electric impact will nut break the lug nuts free.
I use a Snapon 18 volt impact and it works fine with a plus 600 ft lbs breakaway force.
Snapon's are very pricey though. Since I bought mine there are several 500 plus impacts on the market, notably Milwaukee with a 700 ft lb model. "If" I were to buy a new one, it would be a Milwaukee, mainly because I have over the past 5 years, switched all my cordless stuff over to Milwaukee.
If you have a lot on one brand battery tools it make sense to look at that line for the impact you may need.