Not sure why anyone would suggest an atty with bottom airflow as they tend to leak when just looking at them, not to mention the OP wanted something for MTL!!! This would "not" be a Tsunami or a Velocity in any scenario....
As to the original request, The best choices you would have right now would be the Origen Little 16 by Norbert or the Nuppin' by Pdib... These are atty's designed for bottom feeding, first and foremost, and for the MTL person would be spot on. The O-16 is pretty much available, but the Nuppin' is about to put back into production for the 3rd and last time due to the "Deeming Regs" from the idiots... There is a list over in Pdib's thread and it will happen when it hits 100 requests... That should be in the next few days...
You tried the Tsunami for MTL? I have, as for leaking, While I do have one that matches your description on the leaking it is flawed from factory, my second one is quite leak resistant. Also it was a fishing answer. Not knowing budget, or other specifics, and per his requested and statement "wild hair" for a measly 20 buck investment WTH. The Nuppin two post?
After his answer I'd probably suggest a Snapdragon, Manta, maybe even a stumpy I'll also add The Aeronaut in the mix with extra flow tubes. Extremely leak resistant, multitude of AF options one of the better Flavor atties.
My personal experience is I'm sort of the "wild hair" kind of vaper. Plenty of times I'm sucking on a Kayfun, Attaman II, Phenomena, or some such other tank, Other times might be a Snapdragon, Narda, Chalice III, or even a Nuppin. Yea and even MTL on one of my Tsunamis, which is a surprisingly good vape Single coiled & shut down tight. Other times, I get a bit of that "wild hair" And I'm hammering my Haze tank, Velocity, Revolt, maybe a phenol, No name, or one of a fair number of others.
Of the 400 or so atomizers I have and use, the Tsunami might not be the best MTL, maybe not the best for flavor, might not be the most leak resistant I have. However wrap a single coil of 28g, pop the normal drip tip adapter in it, shut down the airflow to whatever suits you from 99.9 closed or wide open if ya get a "wild hair" and you end up with a fairly OK vape for around twenty bucks. And as a bonus it is extremely nice quality & machining.
Oh, and if you want to dial the Tsunami up a notch in single coil MTL mode get/make yourself a chamber reducer.