The problem with this is that we have the physical model of Ford so ingrained within our Indyverse, that we automatically start going towards actors who resemble Harrison.
I liked the choice already mentioned of Clint Eastwood, especially using 20/20 hindsight now and knowing how well the man has aged. Although I wonder if audiences back then would have been taken out of the illusion, seeing "Dirty Harry" with a bullwhip? I mean, we already knew Harrison, but for whatever reason, I never once thought "Hmmm, what is Han Solo doing in the jungle?". Strange.