An election to waive exemption (Also known as an option to tax) has to be made within 30 Days of the date from which it is to take effect, ie it cannot be back-dated to more than 30 days. If you have made any exempt supplies since the purchase of the property in question, eg, charged rent etc, there will be a restriction in your ability to recover all the input tax suffered by you on the purchase.
Commercial properties and VAT is an immensly complicated subject and you are strongly urged to seek expert advise from those who specialise in this field.
One possibility to consider is to lease the land to your company. It is the company who can then decide to construct a building thereon at their cost. They may be able to recover all input tax incurred on construction costs under their own VAT registration. This is done under normal business rules and not under the option to tax rules. But this should be reviewed in conjunction with other related issues.