I seriously think brands that specialize in cloning, are either too trash to even bother with litigation, make it seem that the clone is very limited and not worth the trouble, or do it properly and either communicate with the origin, or "pay homage" to something very much out of production. (I'll let you fill in the blank to whom belongs in each category..)
Like, it would still probably be illegal to make a fliptop combo, called the B-15 and sporting a Ampeg logo but not illegal to shove a solid stage B-15 preamp into a stomp box. The "likeness" of a design can go a long way, even if the schematic is off by a couple components.
Best bet is, to come up with something original, possibly stemming from something you like. The only scenario I see a 1:1 copy being ok is, if NO profit is made, created for personal use, I wouldn't even go as far to use it in a paid gig/studio time
Like I said, cloning is a touchy subject.