Had Dipika been evicted instead of Neha, the following would most likely have occurred:
(a) With nobody to babysit/mother Sree and support him in all wrong-doings, he would have mellowed down much earlier (as he himself asserts that asking initially to go home was just a strategy, don't think he would have actually left). Besides, today's jail scene proved that Sree is capable of lot of acting to display hurt/intense anger etc.
(b) Karanvir would still be with Celebs as he joined Deepak & Surbhi basically because of Dipika and Sree's behaviour.
(c) With Neha and Karanvir giving a fierce competition in tasks, commoners would have no reason to mock celebs with the statement that only commoners are surviving due to their efforts while celebs only due to existing fan-base. In general, there would have been better respect among housemates.
(d) With no extreme actions/reactions from Sree and nobody to target for evoking either anger or tears(it was evident that no adverse comments could break Neha's strength, ditto Jasleen for a long time), Rohit, Deepak and Surbhi would have been within limits and would be much more tolerable.
(e) Neither was Neha's focus one-sided, nor was she judgmental so she could have been a good friend to people like Jasleen who got isolated and bullied.
(f) In absence of fights/cursing,lighter BB12 moments available in Voot would have been shown; atmosphere inside BB house would itself have been happier and more fun moments would have been created. Humorous people like Romil would have come to the fore and Deepak's/Jasleen's singing talent would have been highlighted.
In short, BB12 wouldn't have been the failure it finally turned out to be!