Your concerns are duly noted, however misplaced they must be.
Firstly, you ask who am I to decide the fates of Romans. I am a Senator, and if it pleases the Gods I shall soon be a Consul. Of course I have the authority to dicate the lives of our citizens, as do all Senators. The idea that all citizens have a right to entirely choose their own course is simply not the case, we are a republic, not a democracy. Secondly, I am not ''forcing'' anyone to do anything, I am merely designing policy to encourage a transition in our demography which I believe in the long term will be extremely advantageous to our great Republic. Should they choose to do so, rural citizens may continue to work the land, even if they are not necessarily its owners. However, if they would prefer to migrate to our booming cities to seek employment they may choose to do so. Here they might start businesses, or take on an apprenticeship and learn a trade, this will be beneficial to our economy.
As for your other points, as I made clear earlier I advocate increasing the grain dole. This is a free hand-out of bread to citizens who cannot afford to feed themselves. This will act as a buffer, preventing these migrants from starving while they find work. At first, the cost of this dole may be large, due to many claimants seeking to adjust, but within a few years it will be substantially lessened as these find work and become self-sufficient.
I do not advocate directly increasing the taxation of the large plantations that will form, however due to the economies of scale they will produce, their costs will decrease and they will be able to sell their product more cheaply. Large-scale farming is simply much more efficient then the sea of small-holdings the Grachii Reforms would inflict upon us. Not limiting the ownership of land will also provide a financial incentive for the plantation owners to further expand their plots, which will cause more land to be cultivated, and thus more food produced, and of course, more tax collected for the Senate.
The Republic will quickly adapt to these changing circumstances, and the result will be increased wealth and increased food production to the benefit of all.