Deckers don't really benefit from more flexibility on deck construction. You can already get almost whatever array you want with the current options, with a soft link to Device Rating and Programs. As Attributes get higher so does DR and # of Programs, along with increased cost. And I'm not sure that giving new players a complete custom deck construction option is a good idea, just too many traps for new players. All 5s with a DR1 and no programs for 200 BP for example. Or all 3s and a DR and Programs of 5 for 234? BP. Too much potential for overspending on one area and underspending on others, unless BP are trivial costs and every decker can start with a Fairlight Excalibur equivilant.
The point is to provide a more manageable upgrade path for deckers, not to create a bunch of extra work at chargen. Besides, if you costed it properly, there would be no benefit to building your own at chargen anyway. But once play started it would be quite nice to be able to tinker with your deck and upgrade it piecemeal like a Sam does with his suite of cyberware, instead of trying to save and buy a whole new deck.
My thinking was to make Device rating the gateway for build points. First you upgrade your DR and that gives you more headroom to upgrade the other parts. Of course these upgrades would be more expensive than the "Increase a Matrix attribute" mod from data trails, but would not incur the same penalty either. These are not hardware tricks and hacks, but fully functional upgrades.
OK, Here goes my first attempt:
Upgrading Device rating sets your cap on how many build points you may ADD to your deck. Upgrading DR does not give you any points by itself.
DR1: (52 max BP) - $15,000 - aka scratch built)
DR2: (73 max BP) - $20,000
DR3: (94 max BP) - $25,500
DR4:(115 max BP) - $39,250
DR5: (136 max BP) -$54,375
DR6: (160 max BP) - $73,875
BP cost for upgrading a specific attribute depends on which attribute you're upgrading
Program Slot: 5 PB per slot
High hand: 6 BP per point
Second: 4 BP per point
Third: 3 PB per point
Fourth: 2 BP per point
The cost of adding build points to your deck increases with the total BP value of your deck.
Cost per BP
15-50 - $1000
51-70 - $2000
71-90 - $3500
91-110 - $5000
111-130 - $7500
131-150 - $10,000
151+ - $20,000
A few addendums -
#1 Program Slots cannot exceed DR
#2 The High hand cannot exceed DR+3 unless you have a fixed array, then it can go up to DR+4 (fixed deck construction rules TBD)
#3 It should go without saying, but I'll say it anyway. Your low matrix attributes cannot be raised *higher* then the high matrix attributes.
All this will closely match the cost of configurable decks in the CRB and roughly equate to the configurable decks in Data Trails.
So for example, if you had the headroom already from upgrading your DR and you wanted to upgrade your highest matrix attribute by 1 point it would cost 6 build points. Assuming you had a 100 BP deck already, those 6BP would cost you 6BP x $5000 = $30,000.