electric scooter battery powerpack - mixing cells?

im in the working of making a new power pack, upgrading the old pack from 13s to 16s to be able to keep a target speed that is the limit of my "ev-vespa" the limit is 45km/hr but have a hard time even driving 30 uphill. that aside.

the pack it self is a 16s and between 12-14 pr cell.
got around 500 cells mostly from electric bicyle.
the target is about 30-33amp at 60V nominal. so we are talking about 2.75amp draw pr cell at worst. and at best. 2.14amp on average.

most cells is about 2200mah each. so we are little over 1c of discharge. would there be any problems mixing cells from mostly samsung, sanyoand some unnamed brand that don't have any cell type writen on them.

sanyo: UR18650ZYT25A
samsung: N18650k P030
samsung: ICR18650-22F
to name a few
a guy that works with powerpacks for bicycle saids i should never mix brands and last 3-4 letters/numbers like T25A and P030 should never be mixed in the same cell in parallel.

what are you guys thoughts?

The reason for not mixing is due to the load current. You want "all" cells to push out the amount of current across the whole load curve for something like this. If you are going to be pulling sub-C rates, then it's not so critical to mix them as they aren't pegged at their max.
An example would be matching a V-6 engine with a V-8 engine. when they are both spinning at 6k RPMs, they will put out way different power levels. But both will be able to output 75hp at relatively low RPMs and both will run cooler and safer.

With that said, it depends on what your max Amps are going to be. If sustained max amps is much lower than the max and burst Amps is close or at the lowest cells max rating, then you should be fine.
But, if all of them will be pegged and beyond under surge, then no, you don't want to mix them. A cell that's designed to run at 25C under surge will not fair well under 30C bursts.