It's the approach taken by the late Peter Goldfield when using Rodinal, so has been around a long time.
When I was using Rodinal with APX100 or Tmax100 ssentially I used 1:50 dilution for contrasty situations and 1:25 in flat lighting, I used to use a dilution of 3:100 for Normal lighting. This approach works best with highly dilute developers with low Sulphite content such as Rodinal & HC-110. I have the dilutions and times I used for N-2 through to N+3 in a notebook in my darkroom.
There's no downsides Mike, unless you say the more concentrated dilutions are less economic.
I've never had issues measuring the small volumes need with Rodinal or these days Pyrocat HD, while some use a syringe I've always used the small graduates that came with Photocolor E6 kits.
The notion of using Rodinal at different concentrations for high or low contrast situations actually goes back to datasheets produced in the 1960's and earlier. In fact Agfa were recommending different dilutions to increase or decrease density and so contrast over 100 years ago. Photo-chemists were writing about the effects of greatly diluted developers,J Sterry talks about developer exhaustion and bromide build up as a way of controlling contrast in 1900, and Dr Momme Andresen mentions dilution in his 1905 Agfa Photo-Handbuch and of course he's the chemist who formulated Rodinal and the use of p-Aminophenol.
Use of higher dilutions to control contrast has been around for a long time. The theory is that the developer will exhaust itself much faster in the high values, while the shadow areas continue right along. Various development techniques like EMA, stand, etc, will also affect overall contrast. That said, use a pyro-based formula and you won't need to worry so much about hot highlights!
I have been doing this with my developer of choice, ID11, for a long time with 120 and 35mm film.
HP5 in very bright contrast (rated 200) gets 14 minutes in a dilution of 1+3.
In hazy light (rated 200) it gets 14minutes in 1+2.
In dull light (rated 400) it gets 14 minutes in 1+1.
Foma 400 gets exactly the same treatment -same exposure, same dilutions, same times.
FP4, rated 64 gets 12 minutes for high contrast, in 1+3.
Rated 64 gets 12 minutes for hazy light, in 1+2.
Rated 125 gets 12 minutes for dull light, in 1+1
For large format I tend to stick with the above, but do use other films as well.