Response 7 should be well enough and allows for later modification up to rating 10 (absolute maximum) (you can only ever upgrade commlinks by 3 points max)
Not quite... it's maximum of +2, so he'd need Response 8. The Renraku Suterusu (Response 8, Signal 7) would fit the bill perfectly, since he's got no Availability limits..
Also we are allowed to take hacked programs at character creation.
Big question
here is... will your GM enforce Program Degradation?
--If so, it's going to ding you in the long run if you get too many of them. Probably only worth it for programs you plan on upgrading later.
--If not, then get everything you can at Rating 10, Optimization 2 and follow the below advice. Optimization means you don't have to spend that 192,000¥ on upgrading to Response 10.
Either way, Optimization 2 is still a good idea.
Also, be sure to slap Ergonomic on Analyze, Browse, ECCM, Edit, Encryption, Purge, Scan, and Stealth, as well as putting Mute on Edit, Exploit, Spoof, and anything else that might be used in a foreign node.
--- --- ---
Non Degrading Programs Advice
1) Get "War!"
2) Buy a Renraku Suterusu - 32,750¥ - 40F availability - Response 8, Signal 7.
3) Get System 8 - 32,000¥
4) Get Firewall 10 - 50,000¥
5) Buy every program you might ever want a Rating 10, Optimize 2.
6) Profit.
Total cost = 82,000¥ plus programs.