the truck weighs the most when parked,,, rolling loads weigh less - newark airport's o'nite parking ramp was 18" 4,000 psi @ 28d - load transfer dowels transverse & longitudinal as i recall,,, seems to me 10"'ll work fine,,, recyc conc for base over fabric - either keyed or doweled...
IF the water seepage's as small as you say, i'd favor the polyurethane method,,, get someone who does epoxy injection - prime resin makes a great product - you also don't mention block of pcc - that makes a difference, too,,, soil acids & water'll eventually reduce block to crumbs,,, haven't...
you don't mention whether the basement walls are of block or poured concrete,,, if concrete & water's coming in thru the cracks, you can probably have the crack injected w/hydrophyllic polyurethane & that'll stop water infiltration,,, if block, your choice is excavating outside down to 1/2h of...
we JUST replaced the tile system on section of the manassas, va, battle street train station,,, these tiles were approx. 12"x12" & had, over 3 years, loosened to form a tripping hazard,,, they were replaced w/the vanguard system ( 5 yr. guarantee ) out of washington,,, as i understand...