Of course redeveloping Goodison Park is possible.
Whether it makes short term economic sense is the question.
'Short term' being key under our current regime and setup.
Well, in the long run we are all dead. But still...
So we have ca. 39000 capacity at the moment and average attendance is 38,000-ish? The two 'heritage options' on the proposals above envisage 43,000 - 53,000 and a (perhaps not 'official') cost of 100 million has been mentioned.
To pay off that 'investment' in increased attendances would require around 2,500,000 additional match-day seats sold. At 4,000 extra seats it would take just above 600 matches sold out and with 14,000 extra seats it would take around just under 180 matches sold out.
Of course this is not including any 'extra' costs involved, such as interest on loans or the opportunity cost of other things that could be done with that money, or any 'extra' revenue, such as corporate boxes, naming, etc.
So around 30 years to pay off investment on smallest idea and around 9 years at the next smallest.
(Non-sold-out matches, reduced season ticket average prices and kid's prices would of course extend that timescale. I didn't do the sums on the larger attendances as those are the kind of stadium sizes that have been mentioned before and anything over 53,000 sold out seems extremely optimistic.)
Of course, in reality there is not a do-nothing option for 30 years so at some point an investment of some kind is going to have to be made.