Some thoughts:
big bed so want reasonable rapids, say 10m/min (traverse 8' in 15sec) and 3m/min cutting speed max.
assume 25kg gantry

Force(friction) = mass * g * friction coeef = 25 * 10 * .01 (skate bearings) = 2.5N

Force(accel) = mass * acceleration. Assume acceleration time for rapids = 0.5sec = 0.5m/sec^2, cutting =0.1sec = 0.33m/sec^2 so take accel = 0.5m/s^2 then force = 25 * 0.5 = 12.5N

Cutting force for wood, say 10N max

Therefore force on belt = 2.5 + 12.5 + 10 = 25N, design for 50N cutting, 30N rapids (actually spilt equally between red and white belts)

pitch of HTD belt = 5mm = 2000teeth/min rapids, for 10t pulley = 200rpm, 60rpm for cutting. 200rpm = 666 fullsteps/sec
Requred resolution = 0.1mm, 1 turn of pulley=50mm so need 500steps/rev = 1/4step microstepping.

design torque = 50N @ 7.5mm radius (10t pulley) = 0.38Nm @ 60rpm, 0.23Nm @ 200rpm... a 1Nm motor should acheive this.

Peak torque on 25mm wide 5mm pitch HTD belt is 34N, but this is split between two belts so should be OK. If not will have to go to a wider belt.. Several suppliers, such as Gates-Europe, do HTD5 belts in open-ended style up to 150mm wide but you'd have to make your own pulleys above 25mm.

Belt tension required is around 130kgf

Belt data from gates-europe and spd. However open-ended belting is only available in 100m rolls, so this might not be as cheap as you might think!