In what way is the Speedster not suitable for touring? We have a 2009 Speedster Co-pilot that we've done several shorter tours (3-7 days) on and have been very happy so far. This winter. we plan to take it to New Zealand for a couple of months touring (during their summer). There's not much that I would want to change on it to make it any more ideal for this purpose.
I looked up some older model years of the Speedster and they all seem to have V-brakes, plus rack and fender mounts. Your Speedster may have a carbon fork, but you could easily get a steel fork (you're already planning to change the fork on the Ibis, so this would be a similar cost). The lack of water bottle mounts is easily fixed with some sets of Zefal Gizmo bottle cage mounts,
see here, we have three sets of these on our Speedster to put the Stoker's 2 bottles in more sensible places than the stock braze-ons and to attach our big pump to the bottom tube. Even if your frame can't take a rear disc brake then I wouldn't worry too much about it, we have a rear disc in addition to the two V-brakes, but half the time the disc brake is not even on the bike. It's only needed for really long mountain pass descents (500+ m of vertical descent on a twisty road - on a straighter road or one with less vertical drop then I don't think it's necessary) - so depending on where you're going, there's a good chance that you won't need a disc.
If you do put a disc brake on either bike and have problems with it interfering with a pannier rack, then a company called Tubus makes a quick-release axle mounting kit for fitting racks to bikes without braze-ons. We use a set of these bolted to the regular braze-n mounts because they move the rack mounting point further back so that it doesn't interfere with our disc brake (an Avid BB7). I have no experience mounting a front rack around a front disc - I would say switching to front rim brakes would be the simplest solution then.