Tax saving options - capital gains

First compute the LTCG. He may claim exemption u/s 54F when purchasing another plot. But later if he construct a building and sells flats, they will have to be converted into stock-in-trade.

Yes. That is what the problem. We cant claim Exemption u/s 54F since the amount is invested in land. Also he does not have enough funds for sec 54EC. 

What will be the impact if the sold land is deemed to be stock in trade from the date of its purchase itself ? In that case I guess, the sale consideration would be taxed @ 30% when compared to LTCG tax of 20%. 

Yes, i am wrong but land also is an asset and exemption should be allowed. Not enough funds to construct a house nor buy bonds. Maybe some adjustment in black and white will reduce his liability.

Section 54F --Assessee eligible for exemption : Individual or HUF

But

you can claim exemption u/s 54EC upto Rs.50 lakhs

But 54F exemption wont be available since the assessee purchased land to construct flats and sell.