Hi VeloF'!
You asked...
Should I switch to a platform front rack?
Why not, if you prefer? Vik Banerjee, late of this Forum has long used OMM racks and remains very pleased with them in a variety of applications, including on his onetime Sherpa. See:
http://thelazyrando.wordpress.com/?s=OMMHaving broken a string of top-name aluminum racks, I now prefer steel, but OMM seem to have a very low breakage rate, judging by Forum chatter on the 'Net. They are well-braced and offer some interesting mounting options. See:
http://www.oldmanmountain.com/ Personally, I'm not so enthused about the versions that mount to a quick-release skewer (concerns about overall strength and it seems it could be a bit fiddly when changing wheels with a load on the rack), but in fairness I've not heard any problems reported.
The real key to using a front rack successfully is to avoid having it triangulate the fork between dropout and crown. This is almost never a problem anymore, but sure was back in the day with Blackburn's platform front rack, at least in my experience. It partially "locked out" fork blade flexure, and eventually fatigued itself from the stress.
If I were to go for a platform-like front rack, I'd be inclined toward a Steco in combination with Thorn's Low-Loader MkV front panner racks. I started a topic on Stecos here:
http://www.thorncycles.co.uk/forums/index.php?topic=4294.0 They offer a variety of designs well beyond the one I used to illustrate the topic.
An alternative might be the Surly Nice Rack (Front). Many people use them and are very happy with the design and performance. I am one of the few who was terribly unhappy with mine and sold it on. Why? I loved the two-tier bag mounting option, but there were problems. While the rack was very stiff vertically, I found the flat mounting brackets offered little resistance to lateral movement in my use, so the rack wobbled no matter how tightly it was fastened.
That said, the OMM front platform rack should accomplish all your goals, though the weight will be carried higher than with low-riders, an advantage for use in brush, near curbs, and other obstacles, but with somewhat poorer handling, a detriment offset to a degree by getting more weight forward overall for a more balanced load.
If you go for the platform from rack, will you also be using a handlebar bag? If not, then a popular option is to attach a rack-top bag (usually intended for a rear rack) to the front platform. It gets the weight a bit lower, and sometimes offers a bit more utility.
Best,
Dan.