Online idler brackets like Flurin's worked better but eventually the belt would stretch and start to wear so your prints would start out great and then eventually over time get worse.
I've used the MXL belt for about a year, then used the GT2 belts for about a year.
Must admit i've never noticed any stretch or wear.
But even so, there are other solutions to the problem - like switching to a much heavier duty belt, e.g. Laszlo's T2.5 belts:
They're tough enough that cutting them with diagonal wire cutters isn't a one-snip job (they're much stiffer too and virtually impossible to stretch).
But given enough funds, multiple start leadscrews should definitely be a nice option.
I'm very interested in how they perform, considering they make the platform way more constrained than a belt-driven system can ever be.
So please post some updates as soon as you get some results!