If you plan to use strictly base malts with a higher enzymatic content, you may end up with a fairly dry beer when using honey as a fermentable ingredient. A portion of your beer wort should be left as unfermentable sugars in order to maintain body, so consider that, and your mashing times and temperatures. Balancing your grain choices will be an interesting task because it helps determine your ABV, color, and body.
You will want to decide the wort/must potential ABV level, style and color, so choose the grains, and then the yeast. You also have to consider whether you'll use rye malt, flaked rye, or a mixture because it makes a difference in your all grain recipe and mashing methods. Flaked rye will have to be combined with an enzymatic base malt in order for the starches to convert to sugar, so it would be reasonable to keep the flaked malt down to a certain percentage and mix with malt.
The 2015 BJCP style description for this is wide open for interpretation, listing a starting gravity of 1.040-1.200 and a color range all the way up to SRM 40. A starting gravity over 1.050 may require extra yeast in order to keep the fermentation going properly, and with the amount of fermentable sugars you plan on, the fermentation temperature should be kept cool (65F or lower) in order to keep any off-flavors or fusel alcohols to a minimum. Consider using yeast nutrient for free amino nitrogen (FAN) as a high gravity wort/must can strain yeast health if not enough FAN is available. Fermaid O or K will do.
Personally, I'd try to keep the gravity levels in the "sessionable" ABV range (5-7%) because a higher gravity fermentation may take longer and might stall out if yeast isn't kept healthy. Higher ABV levels affect drinkability and might require a longer aging time.
Hopping will be next to none as this style is considered more of a malt-flavored mead than a honey beer.
I've also considered braggot to be a medieval drink and using a more modern interpretation of the base British darks or milds would appeal to me, as would using the less attenuative ale yeasts that go with them ... but this is your brew, have fun.
Water can be important. Try not to use tap water unless it's properly filtered for chlorine/chlorine compounds. I would choose a soft bottled water and, at most, add a small addition of balanced calcium salts (CaCl + CaSO4) to the mash water if you're planning on doing all grain for the malt portion. It helps the mash and will provide some minerals for yeast health.
