Depend which angle you look at it.
mp has 20 year mine life and mainly light ree and nolan is 38 year minimum light ree and hree
mp has established supply chain integration and aru could enhanced raw material supply including hree (give mp a bit of diversification and align with America goal to secure hree for defence and clean energy)
both are in tier 1 country
mp existing infrastructure could reduce aru capital cost significantly
etc etc etc so really depends to which side you are looking at. If you think not possible you can easily list many reason to why not. If you think possible you list all the synergies and benefits
but a merger between mp, rare element and ucore would create a vertical integrated supply chain
(20min delay)