They could have just raised grain prices.
> So there is no point
> -in saying USSR would be better had NEP policies been kept
> -after 1928. Instead I would believe the situation would evolve
> -(1) to capitalist restoration or (2) to a huge economic crisis
> -(not discarding a combination of 1 and 2).
(1) had already happened by 1928 (and was solidified by the five year plans) and (2) eventually happened anyway. Other alternatives to Stalin's policies within a bolshevik framework include the models applied in Tito's Yugoslavia and Mao's China.