Well actually it is loading from rom's path thing is only that if you use clrmamepro then you will get warnings and so on since you have more files then expected, so it's easier to have it in separate folder.
The megatech.xml will mirror what's in the megatech.c exactly..
there won't be excessive files in that case (and providing it's properly maintained clrmame won't even need to import that SL), so at least for my MAME use case traversing down to the base rom path would simply be easier for everybody.
quick test of best match -- looking good, would definitely prefer 10 matches like MAME rather than 5 tho. User-friendliness just went up by about 5000% tho :-)