Both the DL and the B12 would work for you. I think the DL may be a hair more comfortable with a passenger. (Been touted in the press as a good two-up bike.)
A stock B12, 2001 or newer (with a slightly larger tank than the 2000 and older. should have adequate range for touring.
I think the DL has a bigger tank.
I'm not 100% sure what 'mods' are typical on the DL 1000. You could probably search for a DL rider board and get an idea of what riders are changing on the bikes, for an idea of what could be 'fixed'.
There are actually a lot of people riding stock Bandits. It's a decent bike as it is. If you want to do some aggressive riding in the twisties, with sportbikes, you CAN keep up if you're a competent rider.
The biggest shortcoming of the stock Bandit that you'll discover with aggressive riding, is the suspension. The suspension can be corrected for pretty modest money. The stock suspension is good for a 120 pound Japanese guy, not worth a damn for us 'normal' people.
Easy suspension fixes are Progressive fork springs.....$70
Maybe a 'Busa shock in the rear, (If you want to fiddle, and save sserious money) $30 or so on Ebay.
Or a Progressive 420, Fox TC, or more exotic rear shock ...$400 up.
The riding postion is good,but a lot of us tweak it with different bars.
The seat may need to be addressed. $130 for a Suz Gel seat, more for Sargent or Corbin.
In reality, probably a majority of us spend $1000 or more on upgrades after buying a B12. $1000 goes a long way on a Bandit.
A lot of the MPG problems come from jet kits and carbs that aren't quite right. (I think!) Most of us want a bit more 'grunt', and smoother power throughout the band, and are willing to deal with lower MPG.
The OEM tires are OK. No sense replacing them until you have to.
When you replace, there's better stuff out there.
The longest 'day' I've done on my B12 is 650 miles. People have done a lot more. At least one guy has done a 'CC50' on a BAndit.
(coast to coast in under 50 hours, documented.)
Either bike will suit your purposes, and be a totally different beast than your H-D.
I like the DL, and thought about buying one as a second bike to explore a bit of modest off road/unpaved stuff. I ended up buying a DR650 as a second bike.......and love it.
FWIW, we had an ex BAndit rider show up with a DL650 at our rally last year. He loved the bike, had bought it in Cal, rode east with the Paper tags on it, and probably had 10000 miles on it before he went back to Cal to get his permanent tag. THEN.....he headed north to ALaska!
We have our annual rally in Meadows of Dan, VA next month.
If you're still looking for answers, or have bought a Bandit......show up!
Some people are riding in from as far as Texas, and parts of Canada.