What I mean by comparable is battery operation together with output. Is there anything even close on the market now or coming out very soon? No lithium-ion. It seems there would have to be a competitor by now and lower in price. Do budget manufacturers just not care about powerful NiMH lights? I care :)
I take it the answer is NO 
I wonder why Fenix is monopolizing on this type of flashlight. Li-Ion is more technologically advanced but it's just not as safe in flashlights for the average user. It sure would be nice to see more TK70 type lights out there, but not with the TK70 price tag. I also wonder how Fenix manages to get that thing as bright as a DRY on nearly 1/3 of the voltage. Is there something I'm missing? I'm sure there is because I'm no rocket scientist 
There really is nothing comparable. Keep in mind that most flashlights are made in China. Where lithium batteries are easier to come by and more common. Therefore it would be dumb to pass up on the higher energy density of LiIon. Budget lights are budget because they dont spend money on R&D. They just clone existing stuff and go with what works... stock drivers, with stock tubes, with stock emitters. They are all the same basically. You can't expect a budget company to come up with something really unique.
However, there is no great mystery to the TK70. 4 Ds in series = 4.8 volts which is more than enough for the forward voltage. All you need is enough amperage and unlike Alkalines, NiMH are able to spew out quite a bit of amps.
I expect the TK70 takes about 9 amps, so with a Vf of about 4 volts maybe, thats about 7 amps coming out of the batteries. My TK70 works even with only THREE D batteries on Turbo. So theres no real problem there.
Actually the best thing about the TK70 is the throw. Lots of budget lights have great brightness, but the TK70s throw is what sold me. Its sooo much better than the DRY, etc.
Just guessing: clone makers might not want to clone the TK70 because of the amount of material the TK70 contains. Clones can be cheap because labour is cheap in China, but if aluminum isn't cheap (I don't know if it is or isn't), then a TK70 clone might not be profitable.
And although the TK70 isn't cheap, it is cheaper than the Nitecore TM11, JETbeam RRT-3 XM-L, XTAR S1, etc., all of which are smaller and possibly cheaper to clone.
With a head the size of the TK70's, do they machine it out of a big 4" diameter bar of aluminum, or is it cast? I would guess machined, in which case there would be a ton of waste. Do they recycle the aluminum that they machine out?
Another factor might be that the clone makers see that many of us flashlight nerds like li-ion batteries, but comparatively few of us like C and D size nimhs, so they don't anticipate high volume sales for a TK70 clone.
"I also wonder how Fenix manages to get that thing as bright as a DRY on nearly 1/3 of the voltage." Light output is produced by current through the LEDs, not by battery voltage. So you could have a million volt battery, but if the driver only pushes one picoamp to the LEDs, you're going to get practically zero light output.
I think Li-ion will continue to become the mainstream. Since China and many other nations have no regulations on Lithium and since it's readily available for them to manufacture batteries with, I imagine sooner or later NiMH will all but disappear. Oh, it will take years and years, but I can see it going the way of 8 track tapes and cassettes. It will be either Alkaline or Li-ion.
Safety is not a concern for the majority of users (I believe). I am not talking about members of flashlight forums, or RC enthusiasts, or people who tend to know the score. I'm talking about the "real majority" of average users, who know nothing about battery technology and who don't care either. "Make it easy for me, sell me a light with batteries and a charger, or sell me a light that takes Alkalines. Don't tell me I have to know something, I have no time for that."
I think that is how the real average user feels and I think that is why Alkalines are still king when it comes to flashlights. No charging, buy them anywhere, throw them in the trash, who cares. Got any idea how many $3.00 plastic Wal-Mart flashlights using Alkalines, are sold each day, compared to the Chinese Li-ion lights or Maglites? I would bet it is an astonishing number.
People wanting to use NiMH batteries are in a minority and I think we are diminishing instead of growing. I think what it will come down to is people will just get used to using Li-ion rechargeables just as they use NiMH. Sooner or later they will be so common they will be plugged in the charger in every kitchen or bathroom, just as NiMHs are.
The lights out there using NiMHs, like the few good ones out there now, (I think) will continue to be sparse.