1. Look up theory on size of organisation / growth / etc. Primary factors influencing size - common sense tells me are - Market / ability to raise capital / short term long term invt / desire of the organisation to grow / ability of mgt (a small shop keeper may not be able to manage a chain of super markets even if he gets that kind of capital - actually if you can study the retails market will help you understand) / long term goals / manpower (Currently it has been predicted that in the next year alone the top 6 IT companies will hire 150000 IT engineers & the total output of IT engineers in India is 125000 - so lack of skilled manpower at at affordable cost can also be reason for not being able to expand) / technology / geography(small percentage) (say you want to create electricity from the sun - lucrative market - but technology does not exist that can help you do it on a large scale / say your country is very small - you would have to manufacture it else where & hence Supply chain mgt / becomes important) & finally political envt (see guru - The Parsi community had the licence & no one wanted to entertain the outsider Gujarati) & economics - If expanding costs more money that it can yield for - its still meaningless business. Ie - my marginal cost and marginal cost must atleast break even - (see the law of price fixation in economics)
I have told you this off the cuff - spk to the higher level managers of your organisation & ask them regarding what are their thoughts.
2. Personnel functions handles the manpower - actually here you can sing the entire / permanent or temporary staff raga & how HR function plays a key role in managing costs.
3. For role of HR - you will have to talk about the how Hr will arrive at the number reqd to support this expansion or contraction & how it plans to add / reduce manpower with least impact. HR to person ratio / communication of expansion or contraction / What culture would it like to have & how to create that culture - Also HR could work with the technology ppl & look at what all can be automated to reduce employee costs / time & create a more effective manpower time usage
4. HR will also play a key role in organising - ie org structure reqd to support the size of the organisation - All hiring must be according to hiring plan & org structure.
5. For factors affecting Hr plan - again budget / manpower sanctioned / HR staff / quality of hR staff / Industry & very importantly the quality of the people at top - a marwadi company owner vis-a-vis an MNC culture even if its of the same size.
I hope this helped