I.
. . . what is the maximum province transfer that you think ought to be possible via Taking 10, with and without an Investiture spell?
For example, taking "5 + (Province Level x 2)" as an hypothetical DDC for province transfers, one could Take 10 on Recognition ceremonies involving provinces (2) without a spell bonus; provinces (3) with a +2 DAC spell bonus; provinces (5) with a +5 DAC spell bonus; and provinces (7) with a +10 DAC spell bonus.
For an other example, taking "10 + Province Level" as an hypothetical DDC for province transfers, one could Take 10 on Recognition ceremonies involving provinces (0) without a spell bonus; provinces (2) with a +2 DAC spell bonus; provinces (5) with a +5 DAC spell bonus; and provinces (10) with a +10 DAC spell bonus.
II.
. . . what is the maximum holding upgrade transfer that you think ought to be possible via Taking 10, with and without an Investiture spell?
For example, taking "5 + Province Level + New Holding Level" as an hypothetical DDC for holding upgrade transfers, one could Take 10 on Recognition ceremonies involving 5 combined province/holding levels without a spell bonus; 7 such levels with a +2 DAC spell bonus; 10 such levels with a +5 DAC spell bonus; and 15 such levels with a +10 DAC spell bonus.
Some samples difficulty ratings:Transfer Minor Province - Lvl 2 = DDC 9
Transfer Moderate Province - Lvl 4 = DDC 13
Transfer Great Province - Lvl 6 = DDC 17
Transfer Minor Holding - Lvl 1 in Lvl 3 Province OR Lvl 2 in Lvl 2 Province = DDC 9
Transfer Moderate Holding - Lvl 3 in Lvl 5 Province OR Lvl 4 in Lvl 4 Province = DDC 13
Transfer Great Holding - Lvl 5 in Lvl 7 Prov OR Lvl 6 in Lvl 6 Province = DDC 17
Transfer 4 No Minor Holdings = DDC 13 (4 No separate checks)
Transfer 4 No Moderate Holdings = DDC 17 (4 No separate checks)
Some sample DACs based on 'take 10':No modifier = 10
Stable, prosperous realm = 14 (Assumes total applicable Prosp, Stab & Court modifier of +4)
Investiture spell only = 15 (Assumes spell bonus of +5)
Stable realm AND investiture spell = 19 (Both of the above)
I guess it depends a bit on the flavour and difficulty one wants, but I don't it is unreasonable to be able to undertake the DDC 17 actions by 'take 10' of one has a happy realm and the support of an investiture spell.
One factor I'm not convinced about is the proposed +5 for uncontrolled provinces and holdings. What is the rationale for these being more likely to require the presence of a cleric?