Actually T2 was already planned and built to also accomodate arrivals - that's why it has two floors. No additional construction works are therefore required. The discussion on what to do with it is still going on, but low-cost/charter remain the most likely option.
A very considerable amount of work would be required to adapt the building and equip it to accommodate arrivals, exacerbated by the need to provide the facilities to satisfy non-Schengen and non-European requirements if it were to be used by LCC/charters.
The very limited space available for vehicle access landside is a further problem. Not insoluble, but given the fall in traffic, coupled with the newly expanded T1 there's unlikely to be the commercial and political will to invest more in developing the site in the short-term.