The idea with higher availability is not bad for this campaign, well IMO rather that allow characters to buy almost anything during character creation, Id give them Restricted gera quality for free for every 50 Karma points they are awarded as a "High power bonus"...means if you hand them 150 karma points, they will also have 3 pieces of top rated gear...
BTW: All4Big suggest giving them some resources as a sum. While 5 milion I see as really a lot of money for single runner, I think that giving this to whole team is much better idea, with allowance of karma/nuyen conversion, this allow them to work out with team equipement.
Also Id stress Team again for players while they upgrade their characters, because efficiency of the team also depends on how good they cooperate and how are they able to support each other in their roles...and teamwork is essential and teamwork would be the reason they survive that long and become HighPowered characters. Just herding team of high power individuals won`t win the price, in such case only with potent leadership...